Why do certain cosmetics cause reactions? – Izland BipBip

The common point between a pschit of perfume, a dab of cream, or a layer on a skin baby? These everyday products can cause dermatitis contact, these reactions skin characterized by redness and itching, without anyone knowing how. But new ones works finally suggest a possible mechanism: the small irritant or allergenic molecules of these products would dislodge the fats protecting the skin cells from immune cells, triggering a skin fight. These results are published in the journal Science Immunology.

Molecules incompatible with known allergic processes

Farnesol is an alcohol present in certain cosmetic products. If it had caused an allergic reaction through conventional channels, farnesol once spread on the skin would have been picked up by local immune cells, such as macrophages. These the latter allegedly ingested and then exposed it on their membrane in order to present it to other immune cells, B lymphocytes (white blood cells). These last would have started manufacturing on measured of antibodies, large molecules designed to trap substances they are specifically designed to recognize. If the consumer, oblivious to the drama unfolding, had reapplied the same farnesol product on his skin, the antibodies would have immediately recognized it, causing the allergic reaction.

Problem: farnesol, like many other molecules, does not cause dermatitis until at least 72 hours. A long delay characteristic of a reaction by T lymphocytes, and no B. However, these molecules are too small and too different from the proteins usually targeted to be presented to T lymphocytes. ” Many small compounds that trigger dermatitis contact allergic do not have the chemical groups necessary for this reaction to occur“, Annemieke de Jong, who co-directed these works. ” These little chemicals should be invisible to T cells, but they’re not. “

Activate the immune system by displacing skin fat

But if the mystery was not cleared up until now, certain cells aroused the suspicion of researchers. Thus, a type of immune cell of the skin (called “dendritic”), as well as epidermal cells (called “Langherans”) are likely to play a role. Because among their arsenal of molecular tools present on their surface is found in large numbers a hollow protein called CD1a, and which may well be able to capture farnesol and the like.

Following laboratory analyzes, the hypothesis is confirmed! The reactions dendritic cells and human skin Langherans at contact different allergenic molecules seem to play a role in these particular allergenic processes. Farnesol, to take his example, is more than twice too small compared to the hollow of the protein CD1a: it therefore nestles there in depth, dislodging the largest fat molecules that usually reside there and cover most of it exterior. Having become accessible again, the CD1a protein then unwittingly becomes an outstretched hand towards the T lymphocytes, which then enter into contact with farnesol and trigger the immune response.

A dozen identified allergenic molecules

If farnesol is taken as an example, it is only a product activating T lymphocytes via CD1a among a dozen identified by researchers (including notably squalene, geranylgeraniol or even coenzyme Q2). These chemicals included Peruvian balm and farnesol, which are found in many personal care products, such as skin creams, toothpaste, and perfumes. These results being from laboratory analyzes and no on patients, the authors remain cautious, however. ” The study paves the way for works follow-up to confirm the mechanism in allergic patients And design appropriate treatments, concludes Annemieke de Jong.

Currently, the only way to stop allergic contact dermatitis is to identify and avoid contact with the offending chemical, or to take corticosteroids in more severe cases. But if this discovery is confirmed, theapplication fats capable of taking over the place of allergenic molecules on CD1a could be a possibility.

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The common point between a pschit of perfume, a dab of cream, or a diaper on baby’s skin? These everyday products can cause contact dermatitis, these reactions skin characterized by redness and itching, without anyone knowing how. But new work finally suggests a possible mechanism: the small irritant or allergenic molecules in these products dislodge the fats protecting the skin cells from immune cells, triggering a skin fight. These results are published in the journal Science Immunology.

Molecules incompatible with known allergic processes

Farnesol is an alcohol present in certain cosmetic products. If it had caused an allergic reaction through conventional channels, farnesol once spread on the skin would have been picked up by local immune cells, such as macrophages. The latter allegedly ingested it and then exposed it on their membrane in order to present it to other immune cells, B lymphocytes (white blood cells). These would have triggered manufacturing on measured of antibodies, large molecules designed to trap substances they are specifically designed to recognize. If the consumer, oblivious to the drama unfolding, had reapplied the same farnesol product on his skin, the antibodies would have immediately recognized it, causing the allergic reaction.

Problem: farnesol, like many other molecules, does not cause dermatitis until after at least 72 hours. A long delay characteristic of a reaction by T lymphocytes, and no B. However, these molecules are too small and too different from the proteins usually targeted to be presented to T lymphocytes. ” Many small compounds that trigger allergic contact dermatitis do not have the chemical groups necessary for this reaction to occur“, Explains in a press release Annemieke de Jong, who co-directed this work. ” These little chemicals should be invisible to T cells, but they’re not. “

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Izland BipBip & sciencesetavenir.fr

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