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NCCIH Clinical Digest

for health professionals

Travel-Related Ailments and Complementary Health Approaches

June 2024
travel related illness

People planning international travel often ask their health care providers about the use of complementary or integrative health approaches for travel-related illnesses and conditions. This issue of the Digest focuses on what scientifically credible research says about some of the herbal remedies, dietary supplements, and other complementary health approaches frequently suggested for travel-related ailments and hazards.

Ailment and Summary of Current Research

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

Strongly urge patients to follow official recommendations, including the use of malaria chemoprophylaxis, and not to rely on unproven “natural” approaches to prevent or treat such a serious disease. 

Read more on what the research shows about complementary health approaches for malaria

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. 

  • No solid evidence supports claims that activated charcoal helps with TD, bloating, stomach cramps, or gas. 
  • No high-quality research has been published on goldenseal for TD. 
  • Claims that grapefruit seed extract can prevent bacterial food-borne illnesses are not supported by research. 
  • 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.

Read more on what the research shows about complementary health approaches for travelers' diarrhea

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.

Read more on what the research shows about complementary health approaches for altitude illness

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.

  • Research does not support the use of acupressure or magnets for motion sickness.
  • 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. 
  • No evidence supports claims that homeopathic products prevent or alleviate motion sickness.
  • 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.
  • 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. 
  • 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.

Read more on what the research shows about complementary health approaches for motion sickness

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.

  • Very little evidence supports the belief that aromatherapy or the herbs chamomile or valerian help with insomnia.
  • 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. 
  • Some evidence suggests that melatonin supplements can help with sleep problems caused by jet lag in people traveling either east or west.
  • 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.

Read more on what the research shows about complementary health approaches for jet lag/sleep problems

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. 

  • 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
  • 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-registered insect repellents.
  • 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). 
  • No evidence supports effectiveness of natural products marketed to repel bed bugs. 

Read more on what the research shows about complementary health approaches for insect 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. 

Read more on what the research shows about complementary health approaches as sunscreen

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.

  • A 2023 systematic review and analysis concluded that echinacea may improve cold symptoms; however, the quality of the evidence was low to moderate. 
  • 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. 
  • 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. 
  • 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. 
  • Probiotics might reduce susceptibility to colds, influenza, or other upper respiratory tract infections and shorten the duration and severity of the illnesses. 
  • The U.S. Food and Drug Administration 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. 
  • 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 vitamin C supplements regularly reduces the risk of catching a cold among people who perform intense physical exercise but not in the general population. 
  • Zinc taken orally, often in the form of lozenges, within 24 hours of symptom onset might reduce the duration of a cold. 

Read more on what the research shows about colds and flu

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.

Read more on what the research shows about COVID-19

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.

The National Center for Complementary and Integrative Health is dedicated to exploring complementary health products and practices in the context of rigorous science, training complementary health researchers, and disseminating authoritative information to the public and professionals. For additional information, call NCCIH’s Clearinghouse toll-free at 1-888-644-6226, or visit the NCCIH website at NCCIH is 1 of 27 institutes and centers at the National Institutes of Health, the Federal focal point for medical research in the United States.


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