What’s the Bottom Line?

How much do we know about complementary health approaches for travelers?

We know a fair amount about complementary health approaches for a few common travel-related health problems, including jet lag and altitude illness.

What do we know about the effectiveness of complementary health approaches for travelers?

Some complementary health approaches may be helpful for travel-related health problems, such as melatonin for jet lag, but most either haven’t been studied for travel-related problems or haven’t been shown to work.

What do we know about the safety of complementary health approaches for travelers?

The safety records are mixed for complementary health approaches for travel-related health concerns.

During your travels, you may develop a travel-related health problem, which could vary from something serious, like malaria, to just annoying, like mild diarrhea. Some travelers seek out complementary health approaches to ward off or treat health issues. The information about these approaches on consumer websites or in advertisements is often unsupported by research and misleading or false.

This fact sheet explains what studies tell us about herbal products, dietary supplements, and other complementary health approaches for travel-related ailments.

Malaria

One of the most serious health concerns facing travelers to many countries is malaria, which you can get when bitten by Anopheles mosquitoes. Many consumer websites promote “natural” ways to prevent or treat malaria, which often involve making dietary changes or taking herbal products.

People who travel to countries where malaria is present should follow official recommendations and not rely on unproven natural approaches in an attempt to prevent or treat such a serious disease.Malaria prevention may involve mosquito avoidance and taking medicine to reduce the risk of the disease.

Vitamin and Mineral Supplements

• Taking vitamin A and zinc supplements may help improve malaria symptoms, but only in malnourished children, studies suggest. There’s no evidence that travelers should be taking vitamin A or zinc to prevent or treat malaria.
• Safety:
  • Large or frequent doses of vitamin A may build up in your body, causing severe side effects.
  • Taking beta-carotene, a form of vitamin A, has been linked to increased risks of lung cancer and heart disease in some smokers.
  • There can be short- and long-term side effects of taking excess zinc, from nausea to lower immune function. Zinc supplements can also interact with several types of medications.

Zika

The Zika virus, spread primarily by infected mosquitoes, isn’t dangerous to most people. In fact, many people infected with the Zika virus do not become sick, and those who do often have a mild illness. However, the virus can be passed from a pregnant woman to her fetus, and infection during pregnancy can cause certain serious birth defects. Pregnant women should not travel to areas where there is a Zika outbreak. Having unprotected sex with an infected partner may also pose a risk.

There’s no vaccine or medicine for Zika. Some consumer websites and YouTube videos claim that herbs or other products, such as activated charcoal and diatomaceous earth, will protect against or treat the Zika virus. There’s no evidence that any complementary health products or practices can protect against the virus or treat an infection. Moreover, most dietary supplements haven’t been tested in pregnant women.

Travelers’ Diarrhea

One of the more common illnesses facing travelers is diarrhea; 30 to 70 percent of travelers, depending on where and when they travel, get it. You can’t escape travelers’ diarrhea by just avoiding certain foods or untreated water—you may need over-the-counter or prescription medications. No complementary health approaches have clearly been shown to be helpful in preventing or treating travelers’ diarrhea.

Probiotics

• The results of studies of probiotics for travelers’ diarrhea have been difficult to interpret because of short follow-up periods, different causes of diarrhea, and differences in the types and doses of probiotics, the timing of their use, and the use of other treatments in addition to probiotics. In its 2017 guidelines for the prevention and treatment of travelers’ diarrhea, the International Society of Travel Medicine concluded that the evidence is insufficient to make recommendations about the use of probiotics for either prevention or treatment of travelers’ diarrhea.
• The U.S. Food and Drug Administration (FDA) hasn’t approved any health claims for probiotics.
• Safety: Probiotics generally have only minor side effects, if any. However, people with underlying health problems (for example, a weakened immune system) may have serious complications, including infections.

Goldenseal

• You may see goldenseal, an herb, being promoted on the internet as a dietary supplement for a variety of ailments, including travelers’ diarrhea. However, there isn’t research to back up those claims.
• Safety: Studies show that goldenseal may increase the toxicity or alter the effects of many commonly used prescription medicines.

Activated Charcoal

• There’s no scientific evidence that activated charcoal, which is made from regular charcoal, helps with travelers’ diarrhea, bloating, stomach cramps, or gas.
• Safety: The side effects of activated charcoal haven’t been well documented but were mild when it was tested by healthy people. Warning: Children should not be given activated charcoal for diarrhea and dehydration. It may absorb nutrients, enzymes, and antibiotics and also hide signs that they are dehydrated.

Grapefruit Seed Extract

• Despite claims that grapefruit seed extract will keep you from getting sick, there’s no research on its effectiveness or safety for travelers’ diarrhea.

Altitude Illness

Altitude illness can occur when you travel to heights that you aren’t accustomed to, usually above 8,000 feet. Your body needs time to get used to the change in oxygen levels. Symptoms of altitude illness can be mild, such as dizziness, loss of appetite, or nausea, but can also become much more severe. There’s little, if any, evidence that dietary or herbal supplements can help prevent or treat altitude illness (also referred to as mountain sickness).

Coca

• Coca tea is often used for altitude illness, but there’s no strong evidence on whether it works or has adverse effects.
• Safety: Coca tea, made from the leaves of the coca plant, will result in a positive drug test for cocaine.

Garlic

• There’s no evidence supporting claims that garlic helps with altitude illness.
• Safety: Possible side effects of taking garlic include breath and body odor, heartburn, and upset stomach. Short-term use of most commercially available garlic supplements poses only a limited risk of interacting with medications.

Ginkgo biloba

• The several small studies looking at whether the herb ginkgo can help prevent altitude illness had conflicting results but were mostly negative. It’s unclear whether the conflicting results occurred because the ginkgo products differed.
• Safety: For many healthy adults, ginkgo appears to be safe when taken in moderate amounts. However, ginkgo may interact with anticoagulants (blood thinners) and other medications. Fresh (raw) or roasted ginkgo seeds can be poisonous.

Vitamin E

• Vitamin E, in combination with other antioxidants, has been studied for altitude illness and is recommended for it on some consumer websites. But the limited research done suggests that it’s not effective.
• Safety: Vitamin E supplements may increase your risk of having a stroke and interact with medications, including a blood thinner, statins, and niacin.

Motion Sickness

Children older than age 2 are the most likely to get motion sickness, but anyone can feel nauseous from the motion of traveling by boat, plane, train, or car. Medications may help prevent the nausea but may also have side effects.

Ways To Avoid Motion Sickness

• Sit in the front seat of the car or bus and, if you can, be the driver instead of the passenger.
• In a plane, choose a seat that is over the wing.
• Lie down, shut your eyes, or look at the horizon.
• Stay hydrated, eat small meals, and limit alcohol and caffeinated beverages.
• Distract yourself with music or a pleasant scent.

Complementary health approaches have been studied or advertised for motion sickness but haven’t been shown to work well.

Acupressure and/or Magnets

• Acupressure is sometimes recommended to prevent or treat motion sickness. It involves pressing firmly down on the inside of your wrist or wearing a special wristband that presses that area.
• Studies are mixed on whether acupressure helps with motion sickness.
• Magnets are also sold for motion sickness, but there’s no research that supports their use.
• Safety: Some magnets may interfere with medical devices, such as pacemakers and insulin pumps. Children may swallow or accidentally inhale small magnets, which can be deadly.

Ginger

• Despite ginger’s reputation for helping with nausea, we don’t have any strong evidence that it helps with motion sickness.
• Safety: The effect of combining ginger supplements and over-the-counter drugs for motion sickness is unknown. In some people, ginger can have mild side effects such as stomach upset, heartburn, diarrhea, and gas.

Other Dietary Supplements or Products for Motion Sickness

• There’s no evidence supporting claims that vitamin B6 or homeopathic products prevent or alleviate motion sickness.
• Safety:
  • Like any drug or dietary supplement that contains chemical ingredients, some products labeled as homeopathic may cause side effects or drug interactions.
  • Taking large doses of vitamin B6 for a year or longer can have side effects, ranging from skin problems, extreme sensitivity to sunlight, or nausea to severe nerve damage.

Nausea and Vomiting (“Morning Sickness”) in Pregnant Travelers

Feeling nauseous or even vomiting when pregnant isn’t unusual.

Following are complementary health approaches studied for morning sickness.

Ginger

• Ginger may help ease pregnancy-related nausea and vomiting. Studies suggest ginger is generally safe during pregnancy, but whether it’s always safe for pregnant women isn’t certain. Talk with your health care provider about using ginger (or any dietary supplements) during pregnancy.
• Ginger can have mild side effects such as stomach pain, heartburn, diarrhea, and gas. People with gallstone disease should avoid ginger. Concerns have been raised that ginger might interact with blood thinners.

Vitamin B6

• The American Congress of Obstetrics and Gynecology announced in 2015 that treatment of nausea and vomiting of pregnancy with vitamin B6 or vitamin B6 plus doxylamine (an antihistamine) is safe and effective and should be considered first-line drug treatment. But before taking a vitamin B6 supplement or doxylamine, consult your doctor.

Jet Lag/Sleep

Jet lag occurs when you travel across time zones and your body’s biological clock hasn’t caught up yet. Jet lag can have different symptoms, such as feeling tired and irritable, having an upset stomach, and having difficulty falling asleep or waking up on time.

Melatonin

• Melatonin, a hormone our body produces and also available in dietary supplements, may help with jet lag, studies show. Study participants who were given melatonin before air travel across time zones reported having less jet lag than participants who received a placebo.
• Safety:
  • People with epilepsy or who take a blood thinner should not use melatonin without medical supervision.
  • Taking melatonin appears to be safe for most people when used short-term; less is known about its long-term safety.
  • Melatonin should not be taken early in the day, when it may cause sleepiness and delay your adjustment to local time.
  • The amount of melatonin in products and the dosages recommended on labels can vary significantly.
  • Side effects from melatonin are uncommon but can include drowsiness, headache, dizziness, or nausea.

Relaxation Techniques

• Relaxation techniques, such as progressive relaxation and mindfulness-based stress reduction, may help with insomnia, but we don’t know whether they help with jet lag.

Other Dietary Supplements and Aromatherapy

• There’s very little evidence that aromatherapy, or taking the herbs chamomile or valerian, helps with insomnia. Kava is also advertised for sleep but we don’t have good research on kava for insomnia.
• Safety:
  • Aromatherapy and valerian don’t have significant side effects. Chamomile can cause allergic reactions in some people.
  • Kava supplements may cause severe liver damage.

Colds and Flu

Your best protection against getting the flu is getting vaccinated. Everyone age 6 months and older should be vaccinated against the flu each year.

Here are some complementary health approaches that have been studied for avoiding colds and decreasing symptoms:

Zinc

• Taking zinc products by mouth may reduce the length and severity of a cold, studies show.
• Safety: Zinc, particularly in large doses, can have side effects, including nausea and diarrhea. Don’t use any zinc products in your nose; you may lose your sense of smell.

Salt Water Rinses

• Rinsing your nose and sinuses with salt water may help relieve a stuffed-up nose, though the research isn’t definitive.
• Safety: If you do rinse your nose and sinuses, use only sterile or distilled water to avoid getting an infection.

Vitamin C

• Taking vitamin C supplements regularly may slightly reduce the length and severity of your colds but not the number of colds you get.
• Safety: Even at high doses, vitamin C supplements appear safe.

Other Approaches for Colds and Flu

• There’s no strong evidence that echinacea, garlic, Chinese herbs, oil of oregano, or eucalyptus essential oil prevent or treat colds or that the homeopathic product Oscillococcinum prevents or treats influenza or influenza-like illness.
• Safety: Some traditional Chinese medicine products may have serious side effects—they’ve been found to be contaminated with undeclared plant or animal material, drugs, heavy metals, or pesticides.

Other Common or Travel-Related Infections

Hepatitis C

• The risk of being infected with the virus that causes hepatitis C, a liver disease, when traveling is generally low. However, you can get it from unsterile needles used for acupuncture, a tattoo, or injection drug use; through a medical procedure; or even from sharing personal items contaminated with infected blood, such as razors or a toothbrush.
• No dietary supplement is an effective treatment for hepatitis C. Silymarin, an extract of milk thistle, has been studied for hepatitis C. It has not been found to decrease the levels of the virus in patients’ bodies or improve their liver function.
• Safety: Side effects from silymarin in people with hepatitis C are infrequent and usually include only mild digestive problems.

Vaginal Infections/Urinary Tract Infections

• In studies, probiotics haven’t been shown to help with vaginal or urinary tract infections.
• Safety: Probiotics generally have only minor side effects, if any.

Insect Bites

Avoiding bites isn’t just for your comfort; bugs can spread a number of diseases.

Mosquitoes and Ticks

You can reduce your risk of getting sick by taking these steps to prevent bites:

• Wear protective clothing, sleep in a screened room or an air-conditioned room with the windows closed, and use a bed net if outdoors to avoid getting bitten.
• The CDC recommends using an insect repellent that is at least 20 percent DEET. It helps to ward off mosquitoes, ticks, and other bugs.
  • Other repellents such as oil of lemon eucalyptus (OLE) or para-menthane-diol (PMD) protect against mosquitoes but may not be effective against ticks or other bugs.
  • “Pure” OLE (an essential oil not formulated as a repellent) hasn’t been well tested and isn’t recommended.
  • Insect repellents made from plants, including citronella products, work for less time than products containing DEET.
  • Neem oil is used in agricultural insecticides and promoted on some websites for people, but there’s no evidence that it works or is safe for people.

Bed Bugs

• The risk of picking up bed bugs when you travel is low, but bed bugs have become a problem that travelers need to consider.
• Many products are marketed to repel bed bugs “naturally,” such as essential oils, but we don’t have evidence that they work.
• Follow steps for detecting and avoiding bed bugs, such as inspecting your mattress and keeping your luggage off the floor or bed. It won’t help to spray bug repellent on your clothing or luggage, and it may pose health hazards.

Sun Exposure

Too much sun can cause skin cancer, the most common type of cancer in the United States. Being near the equator or at high elevation increases your exposure to the sun’s dangerous ultraviolet radiation. A few common medications, including some antibiotics, may make you more sensitive to the sun. You also need to watch for sun reflecting off of snow, sand, and water.

To Guard Against Sunburns and Possibly Lower Your Risk of Skin Cancer

• Use a broad-spectrum sunscreen.
• Limit how much time you are in the sun.
• Avoid peak sun hours (10 a.m. to 2 p.m.).
• Wear protective clothing.

“Natural Sunscreens”

Many so-called natural sunscreen products are available on the internet, along with recipes for making your own and advice on consuming dietary supplements or drinking tea to protect against sun damage. Products containing aloe vera and green tea, among other natural ingredients, are promoted as sunscreens. But studies have not proven that any herbal product or dietary supplement, including aloe, beta carotene, selenium, or epigallocatechin gallate (EGCG), an extract from green tea, reduces the risk of skin cancer or sun damage.

Vaccines

• Homeopathic products called “nosodes” or “homeopathic immunizations” are promoted as substitutes for conventional immunizations. There’s no evidence that they work nor any scientific reason they should work.
• It’s important that you are properly vaccinated against serious diseases before you travel. To find out what vaccines you may need, go to the CDC webpage on vaccines for people traveling outside of the United States.

More To Consider

• Dietary supplements may interact with your medications or pose risks if you have certain medical problems or are going to have surgery.
• Many dietary supplements haven’t been tested in pregnant women, nursing mothers, or children.
• Dietary supplements may contain ingredients not listed on the label, prescription drugs not allowed in dietary supplements, and other dangerous chemicals.
• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

There is little, if any, evidence that dietary or herbal supplements help prevent or treat altitude illness.

Coca

Coca leaf (chewed or made into tea) has been used for altitude illness, but there is no strong evidence on whether it works or has adverse effects. It will result in a positive drug test for cocaine metabolites.

Garlic

There is no evidence supporting claims that garlic helps reduce altitude illness.

Ginkgo biloba

Studies of ginkgo for preventing altitude illness are inadequate to justify recommendations about its use.

Vitamin E

Only one small study has investigated vitamin E, in combination with other antioxidants, for altitude illness, and no significant benefit was observed.

Safety

• Garlic supplements appear safe for most adults. Possible side effects of taking garlic include breath and body odor, heartburn, and upset stomach. Some people have allergic reactions to garlic. Short-term use of most commercially available garlic supplements poses only a limited risk of drug interactions.
• Products made from standardized ginkgo leaf extracts appear to be safe when used as directed. However, ginkgo may increase the risk of bleeding in some people and interact with anticoagulants. In addition, studies by the National Toxicology Program showed that rodents developed tumors after being given a ginkgo extract for up to 2 years.

Although colds and flu are not uniquely travel-related hazards, many people try to avoid these illnesses during a trip. Complementary health approaches that have been advocated for preventing or treating colds or flu include zinc products; neti pots and other forms of saline nasal irrigation; vitamin C; probiotics; echinacea; and other herbs.

Zinc

Taking zinc orally (often in the form of lozenges) may reduce the duration of a cold.

Nasal Irrigation and Neti Pots

Nasal saline irrigation, such as with neti pots, may be useful and safe for chronic sinusitis. It may also help relieve the symptoms of acute upper respiratory tract infections, but the evidence is not definitive.

Vitamin C

Taking vitamin C supplements regularly reduces the risk of catching a cold among people who perform intense physical exercise but not in the general population. Taking vitamin C on a regular basis may lead to shorter colds but taking it only after cold symptoms appear does not.

Probiotics

The quality of the evidence is very low that probiotics might reduce susceptibility to colds or other upper respiratory tract infections and the duration of the illnesses.

Herbs

A 2014 systematic review concluded that echinacea has not been convincingly shown to be effective; however, a weak effect has not been ruled out.

There is no strong evidence that garlic, Chinese herbs, oil of oregano, or eucalyptus essential oil prevent or treat colds, or that the homeopathic product Oscillococcinum prevents or treats influenza or influenza-like illness.

Safety

• Zinc, particularly in large doses, can have side effects including nausea and diarrhea. The intranasal use of zinc can cause anosmia (loss of sense of smell), which may be long-lasting or permanent.
• Even in places where tap water is safe to drink, people should use only sterile, distilled, boiled-then-cooled, or specially filtered water for nasal irrigation to avoid the risk of introducing waterborne pathogens.
• Vitamin C supplements appear safe, even at high doses.

There is no credible scientific evidence or plausible scientific rationale to support claims that products called “nosodes” or homeopathic vaccines are effective substitutes for conventional immunizations.

Many products are promoted as “natural” insect repellents, and their use may appeal to people who prefer not to use synthetic products. Products promoted as natural mosquito repellents include citronella products, oil of lemon eucalyptus (OLE), and neem oil (a component of agricultural insecticide products that is promoted on some websites for home use). Essential oils and other natural products are promoted to repel bed bugs.

Mosquitoes

Laboratory studies found that botanicals, including citronella products, worked for shorter periods than products containing DEET. For people who prefer to use botanicals, the Centers for Disease Control and Prevention (CDC) recommends Environmental Protection Agency (EPA)-registered products containing OLE.

The evidence does not support the use of neem oil as a natural repellent.

Bed Bugs

There is no evidence that the natural products marketed to repel bed bugs are effective. Instead, travelers should be encouraged to follow steps to detect and avoid bed bugs, such as inspecting their mattresses and keeping their luggage off the floor or bed.

Safety

• The FDA has recommended that OLE or p-menthane-3, 8-diol (PMD) not be used in children under 3 years of age.

Complementary approaches that have been suggested for jet lag or other sleep problems include the dietary supplement melatonin; relaxation techniques and other mind and body practices; aromatherapy; and herbs such as chamomile, kava, and valerian.

Melatonin

Some evidence suggests that melatonin supplements may help with sleep problems caused by jet lag in people traveling either east or west.

Relaxation Techniques

Relaxation techniques, such as progressive relaxation, and other mind and body practices, such as mindfulness-based stress reduction, may help with insomnia, but it has not been established if they are effective for jet lag.

Aromatherapy and Herbs

There is very little evidence that aromatherapy or the herbs chamomile or valerian help with insomnia.

Another herb, kava, is also promoted for sleep but good research on its effectiveness is lacking.

Safety

• Melatonin is sold as a dietary supplement; dietary supplements are regulated less strictly than drugs. The amounts of ingredients in dietary supplements may vary, and product contamination is a potential concern.
• A 2017 analysis of melatonin supplements sold in Canada found that their actual melatonin content ranged from –83% to +478% of the labeled content and that there was substantial lot-to-lot variation. Also, 26% of products contained serotonin as a contaminant.
• Melatonin supplements appear to be safe for most people when used short-term; less is known about their long-term safety. The absence of long-term studies, however, makes it challenging to know with certainty the safety and tolerability of melatonin with continued use.
• In a 2019 systematic review of mostly short-term trials of melatonin for sleep problems, the most frequently reported adverse events were daytime sleepiness (1.66%), headache (0.74%), other sleep-related adverse events (0.74%), dizziness (0.74%), and hypothermia (0.62%). Almost all adverse events were considered mild or moderate in severity and tended to resolve either spontaneously or after discontinuing treatment.
• People with epilepsy or who take an oral anticoagulant should never use melatonin without medical supervision.
• Travelers should not take melatonin early in the day because it can cause sleepiness and delay adaptation to local time.
• Relaxation techniques are safe for most people.
• Significant side effects from aromatherapy and herbs are uncommon, but chamomile can cause allergic reactions and kava supplements have been linked to a risk of severe liver damage.

Many consumer websites promote “natural” ways to prevent or treat malaria, which often involve dietary changes or herbal products, such as quinine from the cinchona tree (Cinchona spp.) or extracts and material from the artemisia plant (Artemisia annua L. or sweet wormword).

Travelers should follow official recommendations and not rely on unproven “natural” approaches in an attempt to prevent or treat such a serious disease.

Complementary approaches marketed for preventing or treating motion sickness include acupressure, magnets, ginger, pyridoxine, and homeopathic remedies.

Acupressure and Magnets

Research does not support the use of acupressure or magnets for motion sickness.

Ginger

Although some studies have shown that ginger may ease pregnancy-related nausea and vomiting, there is no strong evidence that it helps with motion sickness.

Homeopathic Products

There is no evidence supporting claims that homeopathic products prevent or alleviate motions sickness.

Pyridoxine (Vitamin B₆)

Although an American College of Obstetricians and Gynecologists 2015 Practice Bulletin Summary recommends pyridoxine alone or in combination with doxylamine (an antihistamine) as a safe and effective treatment for nausea and vomiting associated with pregnancy, there is no evidence supporting claims that pyridoxine prevents or alleviates motion sickness.

Safety

• In some people, ginger can have mild side effects such as abdominal discomfort. Research has not definitely shown whether ginger interacts with medications, but concerns have been raised that it might interact with anticoagulants. The effect of using ginger supplements with common over-the-counter drugs for motion sickness is unknown.
• Taking excessive doses of pyridoxine supplements for long periods of time can affect nerve function.

Many “natural” sunscreen products are promoted online, as are recipes for making your own along with advice on consuming dietary supplements or drinking teas to protect against sun damage.

Studies have not proven that any herbal product or dietary supplement, including aloe vera, beta carotene, selenium, or epigallocatechin gallate (EGCG), an extract from green tea, reduces the risk of skin cancer or sun damage.

Safety

• Experts recommend using a broad-spectrum sunscreen, limiting your sun exposure, and wearing protective clothing to protect against sunburns and to possibly lower the risk of skin cancer.

It has been claimed that a variety of products, including probiotics, goldenseal, activated charcoal, and grapefruit seed extract, can prevent or treat travelers’ diarrhea (TD).

Probiotics

Although some studies on probiotics for the prevention of TD had promising results, meta-analyses have reached conflicting conclusions. It is difficult to interpret the evidence because studies have used a variety of microbial strains, some studies were not well controlled, and the optimal dose and duration of use have not been defined.

Goldenseal

No high-quality research on goldenseal for TD has been published.

Activated Charcoal

There is no evidence to support the claims that activated charcoal helps with TD, bloating, stomach cramps, or gas. The side effects of activated charcoal have not been well documented but were mild when it was tested on healthy people.

Grapefruit Seed Extract

Claims that grapefruit seed extract can prevent bacterial foodborne illnesses are not supported by research.

Safety

• In healthy people, probiotics usually have only minor side effects, if any.
• Studies show that goldenseal inhibits cytochrome P450 enzymes, raising concerns that it may increase the toxicity or alter the effects of drugs.
• Children should not be given activated charcoal for diarrhea or dehydration. It may absorb nutrients, enzymes, and antibiotics in the intestine and mask the severity of fluid loss.
• People who need to avoid grapefruit because it interacts with medicine that they are taking should also avoid grapefruit seed extract.