Scientists find how creams, cosmetics cause skin rash

Henrietta Brewer
January 7, 2020

An allergic reaction begins when the immune system's T cells recognize a chemical as foreign.

But they added that the T cells do not directly recognise small chemicals since these compounds needing to undergo a modification with larger proteins to make themselves visible to T cells.

The researcher whose name is Annemieke de Jong is a Ph.D. and is the assistant professor in the Columbia University of dermatology has said that these chemicals are small and must be invisible to these T cells but that is not the case.


To begin the process of finding alternatives, de Jong and her colleagues made a decision to explore how the skin's immune cells respond to the introduction of the chemicals found in consumer products.

De Jong and her teammates distrust that CD1 a, a copious molecule on the skin's Langerhans cell might be accountable for rendering these chemicals apparent to T cells. In the momentum study, directed with human cells in tissue culture, the specialists found that few regular synthetic concoctions known to trigger hypersensitive contact dermatitis had the option to tie to CD1a particles on the outside of Langerhans cells and enact T cells.

An example researchers used was Balsam of Peru, which is an oily tree resin found in many natural and cosmetic products, toothpaste, fragrances and food and drink flavouring. Within Balsam of Peru, the researchers identified benzyl benzoate and benzyl cinnamate as the chemicals responsible for the reaction, and overall they identified more than a dozen small chemicals that activated T cells through CD1a.


Because the study was only done in the lab and not on people, de Jong cautioned that "we have to be cautious about claiming that this is definitively how it works in allergic patients". Rather, she noted, "the study paves the way for follow up studies to confirm the mechanism in allergic patients, and to design inhibitors of the response".

"Normally, many CD1a molecules are filled with natural blockers in our bodies that would prevent an exaggerated immune response, and those small compounds basically remove those natural blockers" says Dr Marcin Wegrecki, who together with Dr Jerome Le Nours, was part of the Monash University team involved in the study. Essentially, these chemicals became "visible" to T cells by binding to CD1a and caused the immune system to respond.

This discovery raises the possibility that allergic contact dermatitis could be stopped by applying competing lipids to the skin to displace those triggering the immune reaction.


It's always been known that certain chemicals cause allergic contact dermatitis (ACD), but our understanding of why this is happening is still very limited. Topical ointments can help sooth the rashes, which usually clear up in less than a month. In some severe cases, prescription oral corticosteroids may be required.

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