Cosmetic dermatitis is caused by the use of cosmetics (including life cosmetics emolliency, whitening, sunscreen, blemishes, hair care agents, lipstick, etc. and literary cosmetics foundation cream, oil, qualitative powder, water powder, etc.) caused by skin inflammatory reactions, including dyed hair dermatitis, oil dermatitis and cold burn dermatitis. Causes: Cosmetics cause dermatitis in many kinds of substances, mainly the following: 1, antiseptic fungicides such as para-phenols, chloroflumuron, trichlorocarbon toluidine, trichlorodiphenylurea, hexachlorophenol, dithiophenol, etc., of which dithiophenol has a photosensitizing effect. 2, pigment Mostly caused by tar pigment, commonly red 219 (Sudan benzo-naphthol), red 505 (Sudan II), red 221 (toluidine red), yellow 204 (quinine yellow). 3, fragrances There are two categories of chemical synthetics and natural agents, common benzylic acid, ylang-ylang oil, pure jasmine, bergamot oil, etc.. 4.Cosmetic base lanolin, propylene glycol, surfactant, two-sided active agent, etc. 5.Hair dye mainly contains hydroquinone, which is a strong allergen, cold perm solution mainly contains thioglycolic acid, thioglycolic acid, dilute ammonia solution, fire alkali, etc. 6, containing drugs or herbal cosmetics where chemical drugs and herbs themselves are semi-antigens. The pathogenesis is the same as contact dermatitis, most of them are allergic reactions, type IV allergic reactions, a few are type I and photopathy. Irritants include the stimulation of counterfeit, poor quality and denatured cosmetics, and some counterfeit cosmetics contain lead, mercury and other excessive standards, causing sensitization or irritation. How should cosmetic dermatitis prevent this condition from occurring? Before each use of cosmetics, in order to avoid skin allergy on the face, you can make a skin test first. 1, first apply a little cosmetic to the skin on the inner forearm or behind the ear, observe for 48 hours, if there is redness, swelling, itching and other reactions, should avoid using, if there is no any reaction then the skin is suitable, this is very important! 2, the correct choice of cosmetics, according to their own skin conditions, and take into account the seasonal climate and other factors to choose the right cosmetics, and pay attention to try not to buy products without manufacturer, factory date and other markings, in addition not to change cosmetics at will, in order to reduce the occurrence of adverse reactions. 3, when the face appears acne, furuncle and other skin diseases do not use cosmetics. When using cosmetics after the face appears small red spots or feel a little itchy skin, you should actively go to the regular hospital dermatology, in the facial itching and redness is not good before using cosmetics, so as not to make the original skin disease aggravated, or cause adverse reactions.