Science sub-journal: Finally know why some skin care products and cosmetics are prone to skin allergies.

▎ academic longitude / report: after using carefully selected skin care products and cosmetics, I didn't expect that the skin would turn red, itchy, edematous and rash, which would damage the appearance and even damage the mood.see your doctor and you may be told that these symptoms are allergic contact dermatitis.the cause of skin allergy may be some ingredients in skin care products and cosmetics.however, why those chemicals can cause allergies is an unsolved mystery.because of this, the only way to stop allergic contact dermatitis at present is to find out the sensitizing chemicals and avoid contact with them.} allergens in skin care products and cosmetics are common causes of contact dermatitis (photo source: 123rf). In a paper recently published in science immunology, a sub Journal of science, scientists are expected to bring more fundamental solutions.researchers from Irving medical center of Columbia University, Brigham and women's Hospital and Monash University in Australia jointly revealed the causes of hypersensitive contact dermatitis caused by several common ingredients in personal care products, and proposed new treatment approaches.Dr. Annemieke de Jong, a professor of Dermatology and one of the co authors of the study, has been concerned about the function of immune cells in human skin.in general, T cells start allergic reactions after recognizing foreign substances."however, many of the small molecules in personal care products that induce allergic contact dermatitis are small molecules that lack the chemical groups that trigger the allergic reaction," she explains. "Traditionally, T cells' don't see 'those small molecules.this is not the case."in this work, Dr. de Jong and his colleagues found that a kind of immune cells in the skin epidermis can" see "common chemicals in skin care products and cosmetics such as balsam of Peru and farnesol through the protein CD1a which is intensively expressed on its surface, thus activating T cells.} Peruvian balm is derived from a South American legume plant and is often used as a spice in skin care products and toothpaste. This natural product is a common contact allergen and can cause severe rashes in allergic individuals (photo source: public) CD1a is a kind of antigen presenting molecule. Under normal circumstances, when they combine with lipid molecules produced naturally by skin, natural lipid molecules will prevent the interaction between CD1a and T cells.however, structural biological evidence suggests that allergens such as farnesol can replace natural lipid molecules and embed into the antigen binding region of CD1a."after substitution, the surface of CD1a is visible to T cells and can cause immune response."explained Professor de Jong.} farnesol is "embedded" in the antigen binding region of CD1a (photo source: reference [1]). The exact role of these chemicals in skin allergy patients needs further experimental verification.however, based on the current findings, researchers have seen a new possibility to prevent allergic contact dermatitis: the application of competitive lipids to the skin to replace substances that induce immune responses."this work paves the way for further studies to identify the mechanism of allergic patients and design inhibitors."said the study authors.reference [1] Sarah Nicolai et al., (2020) human T cell response to CD1a and contact dematitis allergens in biological extracts and commercial skin care products. Science immunology. Doi: 10.1126/ sciimmunol.aax5430 [2] Study Explains Why Some Creams and Cosmetics May Cause a Skin Rash. Retrieved Jan. 5, 2020, from