Breakthrough Discovery Sheds Light on Longstanding Skin Rash Mystery

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Science has some good news for those with allergies to personal care products such as lotions, creams, shampoos, cosmetics and sunscreens. A new study published Jan. 3 in Science Immunology answers a longstanding question — precisely how personal care products trigger the immune responses underlying contact allergic dermatitis, the medical name for allergic skin rashes.

“Physicians have known since the 1950s that allergic responses, especially skin allergies, are mediated by T cells. We’ve also known since the 1960s that T cells respond to protein antigens, especially peptides (small pieces of protein),” study co-author D. Branch Moody, M.D., professor of medicine at Harvard Medical School and physician at Brigham and Women’s Hospital, told MedTruth.

T cells, which fall under the category of white blood cells, are key immune system players that target specific pathogens. Some types of allergies, including allergic contact dermatitis, occur when T cells react to a chemical they identify as foreign. According to immunology, however, personal care product chemicals are too small to trigger T cells.

“The question has been: What is the particular molecule in these creams and toothpastes and deodorants that causes the allergic reaction? Because the textbooks would say that T cells only respond to peptides and proteins, and we know that the molecules in personal care products that cause allergies are not peptides and proteins. They’re small drug-like molecules,” Moody, a rheumatologist, said.

The Missing Link

Researchers found that common personal care ingredients, for instance benzyl benzoate and benzyl cinnamate, found in Balsam of Peru, triggered T cell responses by binding with CD1a, a protein found in Langerhans immune cells abundant near the surface of the skin.

Balsam of Peru, a tree resin with a vanilla scent, is one of the most common allergens, perhaps in the top five, study co-author Annemieke de Jong, PhD, assistant professor of dermatology at Columbia University Irving Medical Center, told MedTruth.

“It’s been widely assumed that in order for T cells to see these small chemicals they would have to bind to a bigger protein,” de Jong said. Indeed, the small molecules hide inside the CD1a molecule, making the CD1A molecule more visible to T cells and inducing a T cell reaction.

Since binding with CD1A is reversible, it provides opportunities to produce molecules that could prevent or reverse this process, de Jong said.

She cautioned, however, that this was a preliminary in vitro study — outside the human body — and that further research is needed to confirm that this mechanism operates in human patients and to develop ways to prevent or treat personal care product allergies.

“It’s still too early to advise consumers based on our findings,” she said.

A Small Step Forward for Large Numbers of People

There’s no clear treatment for personal care product allergies. Antihistamines or other drugs can “knock down” the immune system, but the real treatment is to avoid contact with the allergenic substances, Moody said.

Personal care product allergies affect many people. According to Moody, allergic contact dermatitis has been steadily rising for more than 30 years and is one of the most common reasons patients visit health care providers — and even the emergency room.

“It’s really been within the past 50 years we humans have begun routinely applying makeup, suntan oils and shampoos on a daily basis. The skin gets a lot more exposure to both natural and unnatural chemicals that are in these products,” he said.

To the multitudes who suffer from personal care product allergies, even a small step forward may offer a ray of much-needed hope.

By Carah Wertheimer

Carah Wertheimer is a freelance writer based in Boulder, Colorado. Her areas of specialization include food, health, environment, social justice and community reporting. Her work has appeared in National Geographic, The Denver Post, The Daily Beast, the Boulder Daily Camera, Boulder Weekly and other publications.

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