A new scientific study tells us more about how certain chemicals in cosmetics could cause an allergic reaction such as contact dermatitis.
Allergic skin reactions can be caused by many different chemical compounds found in personal care, household products or even cosmetics. However, how they cause this contact dermatitis has long been a mystery.
In a new study published in the journal Science Immunology, American researchers report that they have observed a previously unknown mechanism. It is believed that certain chemicals can displace lipids in certain epidermal cells, activating certain immune cells.
An allergic reaction starts when T cells (called T lymphocytes) in the immune system recognize a substance as foreign. But these T lymphocytes do not immediately recognize the small chemicals. They have to undergo a chemical reaction with larger compounds to become visible to the T lymphocytes.
In this study, conducted on human cells grown in vitro, researchers found that certain chemicals known to cause contact dermatitis can bind to molecules called CD1a, which are found on the surface of Langerhans cells, a type of immune cell in the epidermis. In this way, the chemicals would become visible to the T-cells, triggering an immune response.
In detail, these chemicals include Peruvian balm (Myroxylon balsamum) and farnesol, two aromatic substances classified as allergens and found in some skin creams, toothpastes and perfumes. In total, the researchers identified more than a dozen small chemicals that activated through CD1a molecules T-cells.
“Our work shows how these chemicals can activate T-cells in tissue culture, but we must be careful to say that this is certainly how it works in allergic patients,” says research co-author Annemieke de Jong. She believes that the study opens the way for follow-up studies to confirm the mechanism in allergic patients and to design inhibitors to the allergic reaction.
This study reveals a new treatment route: the addition of competitive lipids to the skin to prevent CD1a cells from interacting with the T cells of the immune system.
Currently, the only truly effective way to get rid of contact dermatitis is to identify the product in question and avoid or by replacing the product.