Like a bag you unpack at the end of a trip,
And you're wondering why did I take all of this;
These things I don't need weigh me down …

Nanci Griffith

A Packing List


I'm not legally qualified to dispense medical advice;
what follows are personal opinions based on my own experience. For a more comprehensive and authoritative view of medical issues as they pertain to travelling, refer to Dr. Stephen Bezruchka's excellent (and wonderfully portable) The Pocket Doctor.

toilet paper, water squirt bottle, antibacterial wipes

You can't depend on finding toilet paper everywhere. You can't even depend on finding recognizable toilets everywhere. The minute you leave "western" civilization, you will quickly discover that considerably more than half the world uses some variant of the squat toilet. These can range from quite modern fixtures to what amounts to an open pit (when on safari in some desert, you likely won't find toilets at all). If you're unfamiliar with the use of squat toilets, your first encounter can be a daunting one indeed! A little advance practice is highly recommended.

squat toilets around the worldBriefly, pants are rolled up to the knees, and the upper part, along with underpants, lowered to the knees (you don't want them around your ankles!). Items capable of falling are best removed beforehand; retrieving them will likely be impractical. You squat by first bending the upper part of your body forward (to maintain balance), then lower yourself by bending your legs, coming to rest quite naturally (and comfortably) on your haunches and legs. Reverse to rise.

Aim is more important in squat toilets than in sit toilets, so don't fire indiscriminately.

Cleaning up in most places will likely not involve toilet paper, unless you brought your own. This is done using a (probably nearby) container to bring water to your waiting left hand, which will splash it on the appropriate areas. A better (more effective, more sanitary) solution is to bring along your own small plastic water bottle with a squirt top, able to direct a stream of water in the desired direction.

Washing one's hands when finished takes on a new importance; locals may well do this with water only, so you might consider bringing your own soap. Alternatives to soap include hand wipes treated with antibacterial solution (ensure that "Ethyl Alcohol 62%" is one of the active ingredients; one good brand is Purell Sanitizing Hand Towels with Moisturizers), and liquid antibacterial cleansers (often available in travel-sized containers), though the latter introduce the challenge of transporting liquids. There is some dispute among experts about the long-term value of antibacterial products like these (and none of them works on viruses anyway); all agree, however, that frequent washing is more important than the choice of ingredient to abet same. Unfortunately, most people wash their hands in a perfunctory fashion that accomplishes little. It should be done, with soap or the equivalent (which suspends the microbes such that they can be washed away), for at least 15–20 seconds, using warm (or cool, but not hot) water, and should include the backs of the hands, the wrists, and under the fingernails.

And now you know why any social use of the left hand is considered impolite in the Middle East, India, and parts of Africa (it's also why punishment in some countries involves cutting off that particular appendage). If you do use paper, do not deposit it in the toilet (unless there's no plumbing involved), or you will probably clog the pipes. There is likely to be a wastebasket handy: the soiled paper goes there. Yes, really.

If you choose to bring your own toilet paper, not an unreasonable option for shorter trips, be aware that a quarter-roll or so, flattened enough to collapse the cardboard tube, will fit into a sandwich-sized Ziploc® bag.

Females who occasionally find themselves a bit envious of the male anatomy's plumbing convenience can approximate same with the use of a pStyle device (read some of the reviews to understand why this is the preferred — and most effective — type); these can be surprisingly helpful in a variety of travel situations, particularly in areas featuring mosquitoes or similar insects, where any opportunity not to uncover unneeded portions of your skin will be suitably celebrated. In such conditions, one of these can literally save your butt!

There's much more to this topic than mentioned here, as there is truly an amazing variety of toilets to be found in the world. Read the delightful — and informative — "Going Abroad" if you really want to expand your horizons.

(chemical or mechanical) water purifier

If you're travelling anyplace where sanitation is even the least bit questionable, this is a must. The problem, and its several solutions, are too diverse to cover in depth here, but you really should learn about this topic: Rob Sangster's book is a dependable reference, and Travel Medicine, Inc. sells a variety of purifiers. Bottled water can be expensive, and not always available (or even trustworthy; in this respect, bottled carbonated water is safer). Chemical additives taste bad, and may have long-term health implications. Mechanical filter purifiers are bulky, heavy, and most don't remove viruses.

Boiling water, though a bit cumbersome, is an excellent method for eliminating infectious agents. There is some debate about how long to do this, but sustaining a strong boil for at least a minute should render water safe to drink. Another argument in favour of packing a simple immersion heater.

The next best choice is probably the venerable 2–3 drops of iodine in a liter (quart) of water, left to stand for 30 minutes. Yes, there's a bit of a chemical taste, but there is with chlorine-based additives as well, and they don't kill giardia. You can pretty much remove both the taste and the colour by adding 50 mg of vitamin C (ascorbic acid) to the water, after it has stood for the treatment period; a flavoured beverage mix containing vitamin C is fine for this. Be aware that iodine stains terribly, and runs like crazy to boot, so pack it accordingly; if your iodine container ever leaks inside your bag, you'll never forget it! You can find de-coloured iodine in the U.S. and some other places, and the regular stuff at pretty much any pharmacy in the known world.

Popular wisdom states that iodine should not be ingested on a long-term basis (more than six months), but I have never seen any reputable data that confirms this. On the contrary, a study of the previously healthy inmates of three Florida prisons who consumed water disinfected with 0.5 to 1.0 PPM iodine for 15 years showed no effects on health or thyroid function. Of 101 infants born to prisoners drinking the water for 122–270 days, none showed detectable thyroid enlargement. Nonetheless, those with thyroid problems might consider alternative solutions.

If you're planning extended travels in areas where drinking water is a problem, consider one of the more recent high-tech approaches. One popular solution for the traveller is that embodied in SteriPEN water purifierHydro-Photon's SteriPEN®, which makes use of ultraviolet light to kill bacteria, viruses, and parasitic protozoa (i.e., everything). This is a fast (under two minutes) and extremely convenient method, but because it requires light transmission, will not work on heavily clouded water; in such cases the water must first be allowed to settle, or filtered (this need not be onerous, and can usually be accomplished with a coffee filter, or even a bandanna; the company also sells a four-micron screen pre-filter that fits most wide mouth water bottles). I prefer their lightest-weight model, the "AdventurerOpti" (shown at left), which weighs 3.6 ounces (103g) with batteries, and measures 6.1×1.5×1.0 inches (15.5×3.3×2.2cm). Its only drawback is the use of CR123 lithium camera batteries (a larger/heavier model using AA batteries is available, but they must also be lithium, eliminating the AA advantage); you'll get about 100 16-ounce (0.5L) treatments from each pair of CR123s. The UV lamp will last for about 8000 treatments, after which you can see what the newer models offer. Lastly, the AdventurerOpti can also be used as a flashlight, though I prefer to save the batteries for water treatment; still, it's a handy emergency alternative.

MSR's MIOX Purifier

Another technology — one used by the U.S. military — is found in MSR's MIOX® Purifier (shown at right). Fairly cylindrical in shape, it measures 7×1 inches (18×2.5cm), and the complete kit weighs 8 ounces (227g). This is essentially a miniaturized municipal water treatment plant that fits in your pocket. It operates by converting a brine solution to a mixed-oxidant (chlorine) solution via electrolysis. The purifier utilizes two CR123 batteries, common salt, and a tiny electrolytic cell; it will treat approximately 200 liters of water on one set of batteries. Using one is not a trivial process: four hours are required for complete treatment (including removal of cryptosporidium). The MIOX costs almost twice as much as the SteriPEN, but can treat about four times as much water for the same battery cost; consequently, it's particularly worth considering if you have a need to treat large quantities of water at a time.

The third recommended solution — which turns out to be the lowest in cost, lightest in weight, and fastest in operation — is the use of an extremely fine filter by itself. The concern here is one of permeability: in order to remove viruses like cryptosporidium and giardia, the device must incorporate no greater than an absolute 0.1 micron filter (the key word here is "absolute", as opposed to the popular marketing term "nominal", meaning "average"; Sawyer PointONE Filteryou need to know the worst case, because that's the virus that will make you sick). The only product suitable for the lightweight traveller of which I am aware is Sawyer's PointONE™ Squeeze Water Filter (pictured at left). Early models of this device came with a notoriously leaky dirty-water bladder (which you squeeze in order to force water through the filter), but they seem to have solved this problem as of 2013 (you can also use third-party bags with an appropriate adapter). This battery-less device, complete with a one-liter bladder, weighs a modest 3.25 oz. (92g). If you pre-clean dirty water as with the SteriPEN, the filter will last for quite a while without clogging up; for extended trips, a back-flushing syringe adds a scant ounce (28g) to the carry weight. If you decide to go the Sawyer route, take the time to study John Abela's detailed report on this equipment, including his ongoing updates, which offer much more detail than I provide here, and some very clever usage tips contributed by himself and others.

A final caution: in environments that are at all questionable, remember to avoid ice (which cannot be assumed sanitary) and reconstituted drinks, and not let unsafe water in your mouth even temporarily (as when showering and brushing your teeth)!

analgesic of choice

Aspirin, acetaminophen [paracetamol], ibuprofen, naproxen sodium, ketoprofen, or whatever, are best (though not most efficiently) carried in their original packaging, especially if you happen to look somewhat "counterculture", and/or expect to meet suspicious border inspectors. Ibuprofen is a good choice if it works for you pain-wise (it doesn't for me), as it also reduces swelling in muscles and tendons, a common byproduct of too much unfamiliar walking.

If you're planning to venture far from civilization, you'll want to carry something stronger, like OxyContin (because aspirin won't help you with a broken tibia). You'll want a doctor to assist you in obtaining such a highly addictive product, and of course you should only use it to help get yourself to proper medical care.

diarrhea treatment of choice

Studies show that 35% of all international travellers (and 50% of those visiting developing countries in Latin America, Africa, the Middle East, and Asia) develop "traveller's diarrhea" (TD). So there's a pretty good chance that this will be a part of your experience at some point, making it helpful to know something about its causes, prevention, and treatment. Several infectious agents, including bacteria, parasites, and viruses, can cause TD. While parasitic TD can occur 7–14 days after exposure, most shows up some time from a few hours to three days. In up to half of all cases, the exact cause is unknown. The most common bacterial cause of TD (20–50% of cases) is Escherichia coli (E. coli), found in soil, water, and milk. Diarrhea caused by E. coli is generally explosive, non-bloody, and accompanied by nausea, vomiting, cramps, and fever. Shigella is the next most frequent (15% of travellers) bacterial cause of dysentery, being common in countries experiencing natural disasters, socioeconomic upheaval, or other conditions making it difficult to procure sanitary food and water. Shigella infections produce bloody and mucus-laden diarrhea, along with fever, cramps, and exhaustion; such severe consequences are usually labelled dysentery. Next in line (2% of cases) is TD caused by the parasites Giardia and Entamoeba histolytica, found in contaminated water. Giardia can cause chronic diarrhea lasting for several weeks, along with vague pain, weight loss, bloating, and fatigue. And there are other bacteria (Salmonella, Campylobacter), parasites (Cryptosporidiosis, Cyclospora), and (less commonly) intestinal viruses like rotavirus. As you might imagine, dealing effectively with all these possibilities is not an easy matter.

tempting … but caution is advised!Prevention should be the first line of defense. Don't ingest (or swim in) contaminated water; see the above discussion of this topic. With respect to food, the traditional traveller's adage ("If you can't cook it, boil it, or peel it, then forget it!") is still valid, but doesn't go far enough (in the light of current research). Heated food should be hot to the touch, and eaten promptly. Be particularly cautious of food from street vendors. Peel your own fresh fruits and vegetables (be especially wary of things like lettuce and sliced fruit, which may have been washed in contaminated water). Avoid dairy products and raw or undercooked meat and fish.

Pepto-Bismol (two tablets four times daily before and during international travel, but not for more than three weeks) can help prevent many cases of TD. In common with aspirin (which shares its active ingredient salicylate), its use should not be indiscriminate: many medications interfere with salicylate; pregnant women, people allergic to aspirin, and those with ulcers, other bleeding disorders, or gout, should first consult a physician; children under three, and children and adolescents with flu or chicken pox, should not take it. Possible (though rare) side effects of Pepto-Bismol include ringing in the ears, and black stools & tongue.

The two most popular prescription drugs for dealing with TD are Lomotil [diphenoxylate atrophine], which essentially blocks your plumbing for a day or two, and Cipro [ciprofloxacin hydrochloride], an antibiotic to kill the bugs that are causing the problem. As with any prescription drug, discuss the use of these with your doctor before taking them or administering them to others (especially children). The indiscriminate use of antibiotics is causing a lot of problems in the world. In some places (e.g., India and Thailand) bacteria have become quite resistant to Cipro; Zithromax [azithromycin] is currently proving an effective replacement, and may now be the best antibiotic treatment for TD.

Be aware that antimotility drugs such as Lomotil (and Imodium [loperamide], an over-the-counter alternative that works better for some people) do not prevent diarrhea (in fact, they may even increase the risk for it), but they provide prompt though temporary symptomatic relief by reducing muscle spasms in the gastrointestinal tract. Don't use them unless access to a toilet is limited (such as during a long bus ride). And never use them for more than 48 hours.

Rice, wheat, potatoes, corn, and chicken are foods known to slow the effects of TD.

As a rule, letting nature take its course is the preferred approach, abetted with plenty of fluid replacement: drink lots of pure water. In more severe dehydration cases, oral rehydration solutions (ORS) — incorporating potassium, sodium, & calcium supplementation — may be more effective. Pre-mixed, packaged ORS (just add water) can be obtained at shops selling hiking supplies; functional solutions can even be mixed yourself, if you have the correct ingredients available. It's important to understand that the prevention of dehydration is the most important consideration: in severe cases, dehydration can be life threatening, particularly in children. Agitation may be an early symptom; severe indications include listlessness and a weak pulse, and are causes for serious concern.

infection treatment of choice

Another prescription drug, Keflex [cephalexin] is one of the cephalosporin antibiotics. It can be used for a wide variety of bacterial infections, including those of the respiratory tract, urinary tract, skin, and ear. Again, consult your doctor for details. Non-prescription triple-antibiotic ointment [bacitracin + neomycin + polymyxin B] — sold as Neosporin, Mycitracin, Topisporin, etc. — will help keep simple cuts and scrapes from becoming infected (those allergic to neomycin can substitute double-antibiotic ointment, such as Polysporin).

malaria tablets

A must in many parts of the world.

mosquito head netinsect repellent, mosquito net

Even if you're not trekking in places like central Australia (with flies so thick that they have been known to drive horses literally mad), a lightweight, over-the-head mosquito net can save you from hotels whose ideas of adequate screening don't coincide with your own. In many areas of the world, you'll want a net large enough to cover your entire sleeping area; Lifesystems' UltraNet (a super-light, wedge-shaped design) is a good bet for the go-light traveller.

Spraying a net, and — for that matter — your clothing, with permethrin will increase their bug-repelling abilities.

For your skin, you need something containing either DEET [n,n-diethyl-3-methylbenzamide] or picaridin [(RS)-sec-butyl 2-(2-hydroxyethyl)piperidine-1-carboxylate]. Much enthusiastic advertising (and popular "wisdom") to the contrary, these are the only insect repellents that have ever been shown effective in controlled, objective tests. Zappers, ultrasonic devices, clip-on repellents, wristbands, botanicals, and special foods & dietary supplements are the stuff of anecdote, not science.

Picaridin (also called Icaridin, KBR3023, Bayrepel, Hepidanin, and Autan Repel) is the more recent development in this field, and considered less irritating to the skin than the time-honoured DEET, to which it provides comparable protection. Both products are considered safe to use, despite the occasional rumour to the contrary, suggesting that DEET is scary stuff (numerous credible tests have confirmed that DEET is safe when used correctly, even for children and pregnant/lactating women; some people do, however, find that it irritates their skin, especially eyes and mucous membranes). Children don't metabolize chemicals the way adults do, so should use no more than a 10% concentration; those under six months old shouldn't use it at all. Effective repellents can be very hard to find in many places, so be sure to bring what you'll need; it is the best protection available against insects that transmit serious diseases, such as malaria, Lyme disease, and Rocky Mountain spotted fever.

With picaridin, look for a concentration of about 20%; with DEET, the higher the concentration, the longer the protection will last; you need at least 10%, though, and anything more than 50% will not extend the protective period.

Don't use repellent on cuts or other wounds, irritated skin, eyes, or mouth (apply to hands first, then wipe on face). There's generally no need to over-apply: use just enough to cover exposed skin. And unless mosquitoes are biting through your clothing (which they will do if the weave is loose and the fit too snug), it's unnecessary to apply repellent to clothed areas. Finally, washing with soap and water will remove repellent after you've returned indoors.

If you're concerned about getting bitten/stung by any of the flying, crawling, & swimming creatures capable of doing so, consider carrying a small Aspivenin® pump. Aspivenin pumpUsed by the French Army, Médicins sans Frontières, UNICEF, Wildlife Conservation International, etc., this clever mechanical device (developed by André Emerit, a French inventor who died in 1997) visibly extracts venoms without damaging the surrounding skin. You can learn more about it, and order one online for about USD$20, from Aspivenin (France) or from Flairpath Marketing (UK). Sawyer Products sells what appears to be a cheaper (in the U.S.) copy of this device: the Sawyer Extractor.

1% hydrocortisone cream (cortisol, a corticosteroid hormone), the highest non-prescription concentration available in the U.S., will sooth bug bites, allergic rashes, eczema, psoriasis, & certain other inflammatory skin conditions.

Finally, in areas with heavy (or dangerous) insect populations, don't neglect to close off pant legs and long-sleeved shirts with heavy rubber bands or bungee cords around the wrists and ankles.

sunscreen, lip balm

Malignant melanoma is a poor lifestyle choice, so heed the Australian sun protection slogan: Slip (on a shirt) — Slop (on some sunscreen) — Slap (on a hat)! To which I would add a fourth: Seek (shade). Seriously, you shouldn't even leave your house without some form of sun protection.

The best sunscreens use avobenzene, zinc oxide, or titanium dioxide to provide full-spectrum (UV-A and UV-B) protection; look for an SPF rating of at least 15, though 30 is better (you needn't go overboard, though: 30 is fine). A good non-liquid sunscreen is the KINeSYS Sun Protection Stick. Be aware that sunscreens should be reapplied every two hours, and those more than 2–3 years old are no longer effective.

When using both sunscreen and insect repellent, remember that the former work by penetrating the skin to create a barrier, while repellents work by evaporation, so apply the sunscreen first. Wait 20 minutes between the two applications (except for sunscreens using physical blocking agents like titanium dioxide), to allow the sunscreen to be properly absorbed by the skin. There is also evidence that DEET (because it is a solvent) reduces the effectiveness of sunscreen by about 40%, which suggests a more liberal application of the latter than usual. Finally, don't use products containing a mixture of repellent and sunscreen; not only is their efficacy reduced, but sunscreen should be reapplied frequently, and this would lead to excessive repellent application.

Both sunscreens and decent lip balms are hard to find in many areas of the world, so bring enough to last you. Because most lip balms contain waxy ingredients, they can also be used to lubricate zippers, and even give your shoes a quick shine!


Although they have cosmetic uses as well, a good pair of high-quality tweezers can be invaluable should you pick up a sliver or need to remove a tick or insect stinger of some kind. Uncle Bill's Sliver GripperThe very best tweezers available (stainless steel Uncle Bill's Sliver Gripper, pictured at left) are inexpensive, incredibly effective, weigh practically nothing, and carry a lifetime warranty. These are available with either a stainless keychain clip (which protects the points) or a small plastic vial; I find the clip more convenient, and easier to clean.

When General Norman Schwarzkopf discovered these (during the Desert Storm campaign), he wrote, "I have never had a pair of tweezers in my life that was worth a damn. Now I do."

bandages (other first aid supplies?)

I like the cloth butterfly-shaped style of bandages (designed for fingers/knuckles): they can handle surprisingly drastic cuts, and are easily trimmed down to smaller sizes as needed.

Consider more extensive first aid supplies if you plan to travel away from populated areas; Dr. Stephen Bezruchka's handy book is an excellent source of this sort of information. And don't feel that you need to purchase a commercial first-aid kit: it's definitely possible to assemble an appropriate one of your own. Here are some effective supplies that are particularly appropriate for the adventurer who travels lightly:

Lastly, remember the first aid applications of other items on this list, such as duct/gaffers tape (which substitutes for moleskin), safety pins (which can turn clothing into a sling), and the aluminum stays used in travel packs (which make excellent emergency splints).

menstrual, contraceptive, and/or prophylactic supplies

Women travelling for extended periods of time might want to give thought to alternative forms of menstrual supplies. Tampons, for example, are difficult to find in many countries, and more likely to be "toxic shock" specials. Travel- (and environment-) friendly alternatives include medical grade silicone menstrual cups (such as the "use-it-forever" DivaCup and the more travel-friendly — and many say more comfortable — "use-one-per-cycle" Softcup Reusable), and washable cotton pads (such as GladRags and Lunapads; expect about three years' use out of these). Some women make effective use of sea sponges, but this approach raises enough health concerns that I am hesitant to recommend it.

Be prepared — in some countries — to meet customs officials who are unfamiliar with tampons, and will want to inspect these peculiar cylindrical devices (I have read reports of them opening each individual one, looking for illicit substances)!

Another approach to menstrual "management" during travel is based on a surprisingly little-known fact: Medically, it is quite safe to suspend menstruation for many months (even years, although I can't recommend this), using regular (constant-dosage) contraceptive pills — not the triphasic versions, which vary in hormone dosage over the three-week usage period. This is ideal for extended travelling, especially in more remote areas. I don't advocate taking hormones for this purpose alone, but a woman using them anyway can easily reap this particular benefit. Simply take the pills continuously (i.e., no breaks or "week off" sugar pills, which produce the drop in hormone level that triggers the period). It is, of course, important to see your doctor first (to confirm that I didn't just make this up), and to have been taking the pill for at least several months before travelling (to check for any undesired side-effects, such as clotting or blood pressure problems).

Condoms brought from home are less likely to break, and more likely to be available; remember, the diseases most often caught during foreign travels are sexually transmitted ones. (And although some seem not to understand this, being "on the pill" does not stop transmission of STDs.) An unlubricated condom also makes a useful rain protector for cell phones & other small items, an emergency water bottle (when inserted in a sock to help hold the shape), and even — when its ends are knotted together — a makeshift "rubber" band.

vitamins, necessary medications

If you need to carry any prescription drug, be sure to bring along a copy of its prescription, both to replenish your supply in an emergency, and to verify your need for something that might otherwise be illegal in a particular destination country. The drug should be listed by brand and generic name, and include the dosage. If you have a serious condition, a letter from your doctor (translated into the local language) is a wise precaution. Carry more medicine than you expect to need, especially if travelling to places with inferior medical standards.

Have your prescription filled in tablet form when possible, as capsules and liquids are less stable, particularly in hot, humid climates.

Even medications like antihistamines (for seasonal allergies), hydrocortisone (for itching and skin irritations), and such can sometimes be difficult to locate, so bring your own if you need them.

If you're diabetic, review the National Institutes of Health's suggestions on travel with diabetes (both video and text B000QGW6NWversions).

farmacia mercado: questionable prescription medicinesAvoid buying prescription medicines from other than known, trusted sources, especially in developing countries, where local pharmacies will compound drugs themselves, perhaps using something like sulfa (to which you may be allergic) as a filler. Counterfeit drugs, and expired drugs "dumped" from the U.S., are also prevalent (sometimes as much as a third of what's available), particularly in Mexico, Thailand, South America (except Argentina & Brazil), Africa, and Hong Kong.

Also, be suspicious of the sterility of products in many parts of the world. If you require syringes for injectable medicines, consider bringing your own (or sterilizing what you are able to buy).

Note that many common medications (both over-the-counter and prescription) used to prevent motion sickness have a mild sedative effect, so can often do double duty as sleeping pills.

jet lag: it's about clocksDealing with Jet Lag: Few topics are as filled with folklore, foolishness, and fake remedies as the relatively modern condition known as "jet lag". And that, of course, means a marketing bonanza: you'll have no trouble finding "homeopathic" potions, (unregulated) synthetic melatonin supplements, and other purported preventatives/cures for the condition. Don't fall for it; none of this stuff is associated with any credible clinical evidence. It's modern "snake oil".

Jet lag is not even a nutritive issue: it's all about clocks. You probably know that your body maintains an internal biological clock (more correctly called the circadian rhythm), located in the hypothalamus, that regulates many bodily functions, and is normally synchronized with the external environmental "clock" (more correctly, the solar rhythm). In recent years, air travel has enabled us to cross many time zones in a disproportionately short period of time, which can cause these two clocks to get seriously out of sync.

If you take, say, a six-hour flight from New York to Paris, leaving at 6 P.M., you might arrive in France at 6 A.M., but you will feel like it's the middle of the night. That's because, back in New York, it is midnight. So you have circadian misalignment: your body's clock is no longer matched to the actual time in your local time zone.

This affects some people more than others, both in the symptoms produced (which can include excessive daytime sleepiness, nighttime insomnia, headache, loss of appetite, gastrointestinal problems, and irritability or mild depression) and in the time needed to reestablish synchronization. Fortunately, our internal clocks are designed to be synchronized on a daily basis: the natural circadian period is actually about 25 hours, so it responds to a variety of stimulii that cause it to be reset each day (normally, by about an hour). These signals are mostly environmental (exposure to light, activity level, eating/sleeping at appropriate times), but there are psychological aspects as well (What time do you think it is?).

So the "fix" for jet lag is rapid entrainment (resynchronization of the biological clock), not popping pills. As soon as you're settled in your airplane seat, set your watch to the correct time at your destination. And then immediately begin thinking that way; don't be constantly figuring out what time it is "back home". To the extent practical, eat and sleep at the correct (destination) times. When you arrive, endeavour to remain exposed to natural light as much as possible. Don't take "naps" in an attempt to fix things. Actively immerse yourself in the rhythms of your new time zone.

There is one important caveat to this advice. The circadian clock is likely to interpret light experienced prior to 5 A.M. or so as a late sunset rather than an early sunrise. So, in our hypothetical New-York-to-Paris example, it would actually be preferable to avoid sunlight at the destination until about 11 A.M. (5 A.M. in New York / circadian time), at least on the first day. But after that, lots of natural light!

Most internal clocks have difficulty shifting by large amounts (more than a couple of hours or so per day). Also, as noted, some people are more resilient than others. So it's not a quick fix. But it's the best fix.

(collapsible) plastic water bottle & cup

Drink plenty of clean water, like your mom told you (or should have), especially in hot weather. How to know if you're drinking enough? Check your urine: if it's not sufficiently clear to read through, you're not properly hydrated. (If you're severely dehydrated, you may need more than just water; refer to the discussion under "diarrhea treatment", above.)

Getting enough to drink isn't always easy, though, depending on where you are at the moment (like a plane, or other than an urban area of a developed country). So carry your own, in your daypack. A recent innovation is the Platypus® collapsible water bottle, which I have found to be surprisingly rugged, solving a longstanding problem of efficient water storage.

Collapsible Swedish FoldaCupA cup is often useful, and can also be used for cleansing purposes in squat toilets. The best collapsible version I've found is the plastic Swedish Fold-A-Cup, standard issue for the Swedish and Norwegian military; it's lightweight (one ounce), durable, stable, leakproof, and will fit in your pocket. If you're planning to make extensive use of an immersion heater, you may want something less likely to melt (and also, alas, a bit more bulky, though if you choose a material like titanium, it won't be any heavier).

half of a Sawyer water bladder

If even a collapsible cup seems too bulky and/or heavy to you, consider borrowing this idea from the ultralight backpacking community: a surplus water bladder (particularly in the smaller sizes), or even a Platypus bottle, can be cut in half as shown here, to make a nearly weightless cup that practically disappears when not in use. It's an inexpensive solution as well: even if buying new bladders, a 3-pack of water pouches yields as many cups for less than USD$3 apiece.

dark glasses, retainer, case

Good sunglasses (with 100% UVA and UVB protection) will save your sight for your retirement years. The eyewear retainer ("Chums" is a good brand) and case may save your glasses. You can dispense with the case (albeit with a bit of extra care) by using an extra sock or two to safeguard your eyewear.

lens cleaning cloth/supplies, copy of prescription (spare glasses?)

Unless your eyeglass lenses are made of uncoated glass (highly unlikely), don't clean them with tissues, or any other paper product (which will abrade the surface over time). Moisten them first, then use a proper lens cleaning cloth (or, in its absence, a clean, soft fabric). Many opticians will supply you with a proper cloth at no charge. Contact lens wearers need to be particularly attentive to appropriate cleaning supplies.

If you wear prescription lenses, and don't carry spare spectacles (or even if you do), a copy of your current prescription could prove invaluable.