Beware the Hidden Allergens in Nutritional Supplements

3 min read

May 2, 2023 – Popular nutritional supplements could be behind your allergic reactions if no other answer seems clear. 

Allergens may be hidden in a range of supplement products, from colorings in vitamin C powders to some vitamins used in hair products and other products, Alison Ehrlich, MD, said at the annual meeting of the American Contact Dermatitis Society.

"In general, our patients do not tell us what supplements they are taking," said Ehrlich, a dermatologist who practices in Washington, D.C. Antiaging, sleep, and weight loss/weight control supplements are among the most popular, she said. 

Surveys have shown that many patients do not discuss supplement use with their health care providers, in part because they believe their providers would disapprove of their use and patients are not educated about supplements, she said. 

"This is definitely an area that we should try to learn more about," she said.

Dietary supplement regulation comes via the Dietary Supplement Health and Education Act of 1994, which defined dietary supplements as a category of food, not as medications. Dietary supplements can be vitamins, minerals, herbs, and extracts, said Ehrlich.

"There is not a lot of safety wrapped around how supplements come onto the market," she explained. "It is not the manufacturer's responsibility to test these products and make sure they are safe. When they get pulled off the market, it is because safety reports are getting back to the FDA." 

Consequently, a detailed history of supplement use is important, as it may reveal possible allergens as the cause of previously unidentified reactions, she said. 

Ehrlich shared a case involving a patient who claimed to have had a reaction to a "Prevage-like" product that was labeled as a crepe repair cream. Listed among the product's ingredients was idebenone, a synthetic version of the popular antioxidant known as coenzyme Q10

Be Wary of Vitamins

Another potential source of allergies is vitamin C supplements, which became especially popular during the pandemic as people sought additional immune system support, Ehrlich noted. "What kind of vitamin C product our patients are taking is important," she said. For example, some vitamin C powders contain coloring agents, such as carmine, a red dye that comes from dried and crushed shells of some bugs. Some also contain gelatin, which may cause an allergic reaction in people with alpha-gal syndrome, she said. 

In general, water-soluble vitamins such as vitamins B1 to B9, B12, and C are more likely to cause an immediate reaction, said Ehrlich. Fat-soluble vitamins, such as vitamins A, D, E, and K, are more likely to cause a delayed reaction of allergic contact dermatitis (ACD). 

Herbs and spices can act as allergens as well. Turmeric is a spice that has become a popular supplement ingredient, said Ehrlich. Turmeric and curcumin (found in turmeric) can be used as a dye for its yellow color as well as a flavoring but has been associated with allergic reactions. Another popular herbal supplement, ginkgo biloba, has been marketed as a product that improves memory and cognition. It is available in pill form and in herbal teas. 

"It's really important to think about what herbal products our patients are taking, and not just in pill form," Ehrlich said. "We need to expand our thoughts on what the herbs are in."