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

Travelers’ Diarrhea

A variety of products, including activated charcoal, goldenseal, grapefruit seed extract, and probiotics, have claimed to prevent or treat travelers’ diarrhea (TD). Counsel travelers about food and water safety precautions. 

Activated Charcoal 

No solid evidence supports 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. Children should not be given activated charcoal for diarrhea and dehydration because it can absorb nutrients, enzymes, and antibiotics in the intestine and mask the severity of fluid loss.

Goldenseal

No high-quality research has been published on goldenseal for TD. Studies show that goldenseal inhibits cytochrome P450 enzymes, raising concerns that goldenseal might increase the toxicity or alter the effects of some drugs.

Grapefruit Seed Extract

Claims that grapefruit seed extract can prevent bacterial food-borne illnesses are not supported by research. People who need to avoid grapefruit because of interactions with medicines should also avoid grapefruit seed extract.

Probiotics 

There is not enough evidence to draw definite conclusions about the efficacy of probiotics for the prevention of TD. Although some studies have had promising results, meta-analyses have reached conflicting conclusions. Interpretation of the evidence is difficult because studies have used a variety of microbial strains; some studies were not well controlled, and the optimal doses and duration of use have not been defined. 

Altitude Illness Prevention and Treatment

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

Many natural products, including coca leaf, garlic, Ginkgo biloba, and vitamin E, have been promoted for preventing or treating altitude illness. However, there is little, if any, evidence that dietary or herbal supplements help prevent or treat altitude illness.

Coca Leaf

Coca leaf, chewed or made into tea, has been used for altitude illness, but no strong evidence has shown that it works or that it has adverse effects. Travelers should be aware that using coca leaf may cause a positive drug test result for cocaine metabolites.

Garlic

No evidence supports claims that garlic helps reduce altitude illness. Garlic supplements appear safe for most adults. Possible side effects 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 drug interactions.

Ginkgo biloba

Studies of Ginkgo biloba for preventing altitude illness are inadequate to justify recommendations about its use. Products made from standardized ginkgo leaf extracts appear to be safe when used as directed. However, ginkgo can increase the risk of bleeding in some people and interact with anticoagulants. In addition, studies by the National Toxicology Program showed that rodents developed liver and thyroid tumors after being given a ginkgo extract for up to 2 years.

Vitamin E

One study investigated vitamin E in combination with other antioxidants for altitude illness; no significant benefit was observed.

Motion Sickness

Complementary approaches advocated for preventing or treating motion sickness include acupressure and magnets, ginger and the bioactive plant compound hesperidin, homeopathic remedies, music and relaxation, pyridoxine (vitamin B6), and vitamin C.

Acupressure and Magnets

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

Ginger and Hesperidin 

Evidence from some laboratory and clinical studies has suggested that ginger might help with motion sickness, but other studies have not found a beneficial effect. Although the evidence for effectiveness of the bioactive plant compound hesperidin (found in citrus fruit) is very limited, one study has suggested benefit for motion sickness. In some people, ginger can have mild side effects (e.g., abdominal discomfort). Research has not definitively shown whether ginger interacts with medications, but concerns have been raised that it could interact with anticoagulants. The effect of using ginger supplements with common over-the-counter drugs for motion sickness (e.g., dimenhydrinate [Dramamine]) is unknown. Taking hesperidin is probably safe, but those taking medications should consult their health care professional about any potential supplement-drug interactions. 

Homeopathic Remedies 

No evidence supports claims that homeopathic products prevent or alleviate motion sickness.

Music and Relaxation 

Some evidence suggests that listening to favorite music can increase relaxation and decrease motion sickness symptoms, and that fresh air, autogenic feedback training, and controlled diaphragmatic breathing can help with motion sickness.

Pyridoxine (vitamin B6) 

Although an American Congress of Obstetrics and Gynecology 2015 Practice Bulletin Summary recommends pyridoxine (Vitamin B6) alone or in combination with doxylamine (an antihistamine) as a safe and effective treatment for nausea and vomiting associated with pregnancy, no evidence supports claims that pyridoxine prevents or alleviates motion sickness. Taking excessive doses of pyridoxine supplements for long periods of time can affect nerve function.

Vitamin C

Although the evidence for effectiveness is limited, one study found that taking 500 mg of vitamin C can help improve seasickness, especially in young adults. Note that in children aged 3 years and younger, the daily upper limit for vitamin C is 400 mg. Too much vitamin C can cause gastrointestinal distress.

Jet Lag and Sleep Problems

Complementary approaches suggested for transient sleep problems that may be related to travel include aromatherapy and herbs (e.g., chamomile, kava, valerian); blue light-blocking glasses, the dietary supplement melatonin; relaxation techniques; and yoga. 

Aromatherapy and Herbal Products

Very little evidence supports the belief that aromatherapy or the herbs chamomile or valerian help with insomnia. Major side effects are uncommon, but chamomile can cause allergic reactions. Another herb, kava, also is promoted for sleep, but good research on its effectiveness is lacking. More importantly, kava supplements have been linked to a risk of severe liver damage.

Blue Light-Blocking Glasses 

Some research has shown that wearing glasses that block blue light for several hours before bedtime can improve insomnia, and one study found the glasses can help with jet lag. Sunglasses can also protect against blue light; purchasing special blue light-blocking glasses is not necessary. 

Melatonin

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

Melatonin is sold as a dietary supplement. Dietary supplements are regulated by the U.S. Food and Drug Administration (FDA), under the Dietary Supplement Health and Education Act of 1994, but the rules are less strict than for drugs, as the FDA generally does not have the authority to approve dietary supplements before they are marketed. The amounts of ingredients in dietary supplements can 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 percent to >478 percent of the labeled content and that substantial lot-to-lot variation was evident. Also, 26 percent of products contained serotonin as a contaminant. Melatonin supplements appear to be safe for most people who use them for discrete periods of time. An absence of studies examining the effects associated with continued use makes it challenging to know with certainty melatonin’s long-term safety and tolerability. In a 2019 systematic review of mostly short-term trials of melatonin for sleep problems, the most frequently reported adverse events were daytime sleepiness (1.7 percent), dizziness (0.7 percent), headache (0.7 percent), other sleep-related adverse events (0.7 percent), and hypothermia (0.6 percent). Almost all adverse events were considered mild to moderate in severity and tended to resolve either spontaneously or after discontinuing treatment. 

Relaxation Techniques, Yoga, and Other Mind and Body Practices 

Relaxation techniques (e.g., progressive muscle relaxation), other mind and body practices including mindfulness-based stress reduction and yoga, and a variety of spiritual and religious practices may help with insomnia, but their effectiveness for jet lag has not been established.

Insect Protection

Many products are promoted as “natural” insect repellents, and their use can appeal to people who prefer not to use synthetic products. Products promoted as natural mosquito repellents include citronella products, catnip oil, and oil of lemon eucalyptus. Essential oils and other natural products are promoted to repel bed bugs. 

Mosquitoes

Some limited evidence suggests that plant-based repellents such as Ligusticum sinense extract, citronella, pine, Dalbergia sissoo, peppermint, and Rhizophora mucronata oils may be effective against Anopheles mosquitoes (marsh mosquitoes). 

Essential oils from plants such as lavender, camphor, catnip, geranium, jasmine, broad-leaved eucalyptus, lemongrass, lemon-scented eucalyptus, amyris, narrow-leaved eucalyptus, carotin, cedarwood, chamomile, cinnamon , juniper, cajeput, soya bean, rosemary, niaouli, olive, tagetes, violet, sandalwood, litsea, galbanum, and Curcuma longa have shown some protection against different species within the genus of Anopheles. It should be noted, however, that repellency effectiveness is difficult to interpret with a limited number of studies and many differences in compound concentrations, dosages, formulations, and methods for assessing repellency. 

Given that product claims have not yet been validated by rigorous research, and that more research is needed, travelers should use only Environmental Protection Agency (EPA)-registered insect repellents.

Botanicals

Laboratory-based studies found that some botanicals, including citronella products, do work but for shorter periods than products containing DEET (N,N-diethyl-m-toluamide or N,N-diethyl-3-methyl-benzamide). For people who choose to use botanicals, the Centers for Disease Control and Prevention (CDC) recommends only EPA-registered products containing oil of lemon eucalyptus and that users carefully follow application guidance on the product.

Bed Bugs

No evidence supports effectiveness of natural products marketed to repel bed bugs. 

Sun Protection

Many “natural sunscreen” products and recipes for homemade sunscreens are promoted online. While there is no evidence that these topical products or formulas offer any protection against sun damage, some research suggests that green tea catechin supplements may help protect against damage induced by ultraviolet light. 

No studies have shown that any other dietary supplements or herbal products, including aloe vera, beta carotene, or selenium, are helpful. 

Colds and Flu

Although colds and influenza 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 influenza include echinacea, elderberry, garlic and other herbs, nasal saline irrigation, probiotics, silver, South African geranium, vitamin C, and zinc products.

Echinacea

A 2023 systematic review and analysis concluded that echinacea may improve cold symptoms; however, the quality of the evidence was low to moderate. Taking echinacea for a short amount of time is probably safe, but some people may experience gastrointestinal side effects.

Elderberry

Taking elderberry may be helpful for cold and influenza symptoms and result in a quicker recovery from illness. However, the quality of the evidence is low because only a few small studies have been conducted. Elderberry flowers and ripe fruit appear to be safe, but the bark, leaves, seeds, and raw or unripe fruit can be toxic and cause gastrointestinal distress. 

Garlic and Other Natural Products

No strong evidence supports claims that on their own, 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. A 2022 review of homeopathic products for colds in children did not find consistent evidence of benefit.

Nasal Saline Irrigation

Nasal saline irrigation (e.g., use of neti pots) can be useful and safe for chronic sinusitis. Nasal saline irrigation also can help relieve the symptoms of acute upper respiratory tract infections, but the evidence is not definitive. 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 water-borne pathogens.

Probiotics

Probiotics might reduce susceptibility to colds, influenza, or other upper respiratory tract infections and shorten the duration and severity of the illnesses. Effects were relatively consistent across different combinations of probiotics, doses, and durations, but the quality of the evidence is low.

Silver and Colloidal Silver

Silver and colloidal silver have gained popularity because of online marketing websites that promote their use for COVID-19. A 2021 review of 16 in vitro and in vivo studies of the effects of silver nanoparticles on respiratory viruses noted that few studies have been conducted in humans. The FDA does not recognize colloidal silver as safe or effective, and it is not known whether colloidal silver or over-the-counter silver nanoparticle products are safe or effective against highly virulent viruses in humans. In vitro testing has demonstrated that nanosilver solutions can be effective against viruses such as herpes simplex virus 1 and SARS-CoV-2, and observations of off-label use of nebulized nanosilver solutions in patients with pneumonia (ventilated), patients with fungal sinusitis, and two non-hospitalized patients with COVID-19 have shown clinical improvements including elimination of infection. This suggests potential benefit of nanosilver solutions for treating respiratory inflammation and infections caused by viruses and/or microbes. Randomized controlled trials would be needed, however, to determine the reliability of these clinical observations.

South African Geranium

A 2023 review and analysis of three studies of South African geranium (Pelargonium sidoides) found moderate-quality evidence that it can improve cold symptoms. Taking South African geranium, also known as umckaloabo, for a short amount of time is probably safe for adults and children. However, people taking blood thinning medications or who have liver disease, asthma, or allergies to plants in the geranium (Geraniaceae) family should avoid taking South African geranium.

Vitamin C Supplements

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 might lead to shorter-duration colds, but taking it only after cold symptoms appear does not. Note that taking too much vitamin C can cause gastrointestinal distress. 

Zinc

Zinc taken orally, often in the form of lozenges, within 24 hours of symptom onset might reduce the duration of a cold. No firm recommendation currently can be made, however, regarding prophylactic zinc supplementation because of insufficient data. When taken in large doses, side effects from zinc can include nausea and diarrhea, copper deficiency, and decreased absorption of some medications. Intranasal use of zinc can cause anosmia (loss of sense of smell), which may be long-lasting or permanent.

COVID-19

A variety of dietary supplements, including elderberry, melatonin, colloidal silver, vitamin C, vitamin D, and zinc, have each been suggested to prevent or treat COVID-19. 

• A 2023 review found no evidence of efficacy for colloidal silver or zinc. 
• Currently, there is insufficient evidence of efficacy from clinical trials of elderberry, melatonin, or vitamins C or D to recommend for or against their use.

References