NCCIH Clinical Digest

for health professionals

Travel-Related Ailments and Complementary Health Approaches : What the Science Says

June 2018

Clinical Guidelines, Scientific Literature, Info for Patients: 
Travel-Related Ailments and Complementary Health Approaches

travel related illness

Malaria Prophylaxis and Treatment

Artemisia (Artemisia Annua L. or Sweet Wormwood) and Quinine

Quinine from the cinchona tree (Cinchona spp.) may be used in combination with other antimalarial medications to treat malaria. There is no evidence that quinine prevents malaria. Travelers should not attempt to use quinine to self-treat or prevent malaria.

Although consumer websites and news stories have claimed that using the herb artemisia alone may prevent malaria, studies show it does not. The World Health Organization recommends against using artemisia plant material in any form (including tea) for treating or preventing malaria.

Vitamin and Mineral Supplements

There is no evidence that vitamin A or zinc prevent malaria infection.


  • The use of artemisia alone has contributed to the increase in malaria parasites resistant to artemisinin.
  • Vitamin A is fat soluble, and large or frequent doses of vitamin A may accumulate in the body and case acute or chronic toxicity. High intake of vitamin A has been linked to birth defects. Taking beta-carotene, a precursor of vitamin A, has been linked to an increased risk of lung cancer and cardiovascular disease in some smokers.
  • Zinc supplements can interact with several types of medications.

Zika Prophylaxis and Treatment

There is no evidence that any herbs or other products, such as activated charcoal or diatomaceous earth, will protect against or treat the Zika virus.


  • The side effects of activated charcoal have not been well documented but were mild when it was tested on healthy people.
  • 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.

Travelers’ Diarrhea


Research on the use of probiotics in treating acute infectious diarrhea is generally positive. Results from studies on preventing travelers’ diarrhea are mixed but encouraging. The U.S. Food and Drug Administration has not approved any health claims for probiotics.

Given current data, it must be assumed that effects of probiotics in any given study are specific to the strain(s) tested.

Activated Charcoal

There is no evidence to support the claims that activated charcoal helps with travelers’ diarrhea, bloating, stomach cramps, or gas. Children should not be given activated charcoal for diarrhea and dehydration, as it may absorb nutrients, enzymes, and antibiotics in the intestine and mask the severity of fluid loss.

Grapefruit Seed Extract

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


  • In healthy people, probiotics usually have only minor side effects, if any.
  • The side effects of activated charcoal have not been well documented but were mild when it was tested on healthy people. 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.

Altitude Illness

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


Coca 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.


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

Ginkgo Biloba

Results from several small studies of ginkgo for preventing altitude illness show conflicting, but mostly negative, results. Whether these differences relate to the different preparations used in these studies cannot be determined.

Vitamin E

Only one small study has investigated vitamin E, in combination with other antioxidants, for altitude illness, and the results were negative.


  • 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 for causing herb-drug interactions, including interfering with the effectiveness of the HIV drug saquinavir.
  • 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 certain conventional medications, including 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.
  • Taking vitamin E supplements has been linked to an increased risk of hemorrhagic stroke. Vitamin E supplements also have the potential to interact with several types of medications, including statins, niacin, and warfarin.

Motion Sickness

Acupressure and Magnets

Using acupressure or magnets is advocated by some to prevent or treat motion sickness; however, research does not support the use of acupressure or magnets for this purpose.


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

Pyridoxine (Vitamin B6)

Although the American Congress of Obstetrics and Gynecology’s 2015 Practice Bulletin Summary recommends pyridoxine alone or in combination with doxylamine 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.


  • Several studies have found no evidence of harm from taking ginger during pregnancy, but it’s uncertain whether ginger is always safe for pregnant women. 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.
  • Excessive use of pyridoxine supplements can affect nerve function.

Jet Lag/Sleep Problems


Melatonin supplements may help with sleep problems caused by jet lag. Travelers report having less jet lag on eastward and westward flights when given melatonin compared with placebo. In a 2007 clinical practice guideline, the American Academy of Sleep Medicine supported using melatonin to reduce jet lag symptoms and improve sleep after traveling across more than one time zone. A systematic review suggested that taking 0.5-5 mg of melatonin appeared to be effective for easing jet lag.

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


  • People with epilepsy or who take an oral anticoagulant should never use melatonin without medical supervision. Melatonin supplements appear to be safe for most people when used short-term; less is known about long-term safety. Melatonin should not be take early in the day, as it may cause sleepiness and delay adaptation 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 are safe for most people.

Insect Protection


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 recommends Environmental Protection Agency (EPA)-registered products containing oil of lemon eucalyptus (OLE), such as the products Repel and Off! Botanicals.

There are no high-quality studies on the effectiveness or safety of neem oil for preventing mosquito bites.


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


Sunscreens are promoted as containing aloe vera and green tea, among other natural ingredients, but studies have not proven that any herbal product or dietary supplement, including aloe, beta carotene, selenium, or epigallocatechin gallate (EGCG), an extract in green tea, reduce the risk of skin cancer or sun damage.


  • 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.

Homeopathic Vaccines

There is no credible scientific evidence or plausible scientific rationale to support claims that certain homeopathic products (sometimes called nosodes or homeopathic immunizations) are effective substitutes for conventional immunizations.


  • Law C, Adler T, Shurtleff D. Discussing complementary and integrative health approaches with travelers. In: Brunette GW, Kozarsky PE, Brown CM, et al, eds. CDC Yellow Book 2018: Health Information for International Travel. New York, NY: Oxford University Press; 2017.

NCCIH Clinical Digest is a service of the National Center for Complementary and Integrative Health, NIH, DHHS. NCCIH Clinical Digest, a monthly e-newsletter, offers evidence-based information on complementary health approaches, including scientific literature searches, summaries of NCCIH-funded research, fact sheets for patients, and more.

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