‘Molecular missing link’: Research explains why some creams cause a skin rash

By Richard Whitehead

- Last updated on GMT

Allergic skin reactions can be caused by many different chemical compounds. ©GettyImages
Allergic skin reactions can be caused by many different chemical compounds. ©GettyImages

Related tags Science

Allergic skin reactions can be caused by many different chemical compounds found in skincare creams, cosmetics and other topical consumer products, but how they trigger the reaction has remained somewhat mysterious…until now.

New research that suggests the way some chemicals displace natural fat-like molecules known as lipids in skin cells may explain how many common ingredients trigger allergic contact dermatitis.

The breakthrough could help stem soaring cases of rashes, lumps, blisters, itchy eyes and facial swellings. It has been dubbed the “molecular missing link​” because it might have brought a new way to treat the condition.

Currently, the only way to stop allergic contact dermatitis is to identify and avoid coming into contact with the chemical that causes the reaction.

Most allergies are attributed to proteins or synthetically produced peptide antigens that set off the immune system.

But chemicals found in personal care products are different kinds of molecules that were not thought to be able to directly elicit a reaction.

Topical ointments can help soothe the rashes, and oral corticosteroids may be prescribed for severe cases, although these can increase the risk of infections and other side effects.

The newly reported discovery raises the possibility that allergic contact dermatitis could be prevented by applying lipids to the skin that compete with and displace those triggering an immune reaction.

Jamie Rossjohn, a professor of biochemistry and molecular biology at Monash University in Melbourne, was part of a team of international researchers investigating the role an abundant protein in the skin known as CD1a could play in allergic reactions to cosmetics.

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​” he said.

Part of the research focused on small chemicals found in many essential oils and botanical extracts such as the Balsam of Peru, an oily tree resin found in many cosmetic products, toothpastes and fragrances, and farnesol.

“Balsam of Peru is used in natural products because it comes from a tree, and isn’t chemically synthesised, so it was very popular. But unfortunately a significant number of people—up to five per cent of the population—are allergic to it because it contains all those small compounds,” he said.

Using a high energy X-ray beam at the Australian Synchrotron at Monash University, the researchers were able to describe the way CD1a and farnesol, another common additive in cosmetics and skin creams, interact at a molecular level.

Marcin Wegrecki, of the Monash Biomedicine Discovery Institute, said the findings provide more clarity about what was happening.

Now we know how some of the compounds found in skin care products and cosmetics can directly interact with human proteins​,” he said.

Despite the known allergy, Balsam of Peru is still used in some products. The researchers are now seeking new molecules that could block the response of CD1a and override the activation of immune cells. Work is currently underway to identify promising compounds.

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