Science: Why do some skin care products and cosmetics cause skin allergies?

In life, many compounds in skin care products and cosmetics may cause skin allergy. It is mediated by T cells and the incidence rate is increasing. However, the molecular mechanism behind it is still to be explored.a recent study in science immunology showed that some components in skin products combine with CD1a on the skin surface to replace the natural fat in skin cells, thus activating immune T cells and causing allergy.DOI:10.1126/sciimmunol.aax5430 CD1a is a rich MHC class I protein in human skin, which can recognize contact allergens and widely exists in skin's outer layer of immune cells such as skin's Langerhans cells.CD1a molecules usually bind the skin's own natural fat to its tunnel like interior.these fats protrude from the tunnel and form a physical barrier to prevent the interaction between CD1a and T cells.The aim of this study was to explore whether known contact allergens bind to CD1a and stimulate CD1a dependent T cell responses.crystal structure of CD1a, Sarah Nicolai and other researchers carried out research on common ingredients in skin products such as Peruvian balsam and farnesol, and used CD1a restricted T cell lines and polyclonal purified T cells from healthy blood banks to detect T cells in vitro.verified that CD1a presented contact allergen to T cells; then, using TLC, MS and other techniques to try to find out the chemical structure of the antigen, found that benzyl cinnamate and benzoate are the antigens of CD1a, and the former has a greater response than the latter.then the common structure and size were analyzed.chemical analysis of antigens in Peruvian balm. In conclusion, researchers have found more than a dozen small chemicals that activate T cells through CD1a.senior author de Jong of the study pointed out that this work confirmed the allergic mechanism and designed reaction inhibitors, which paved the way for further research.however, no patient study has been conducted, so it is uncertain whether it is effective for allergic patients.end References: [1] human T cell response to CD1a and contact derivatives allergens biomedical extracts and commercial skin care products [2] study explains why somecream and cosmetics may cause skin rashes