Cosmetic allergies often cause cosmetic contact dermatitis. Cosmetic contact dermatitis refers to irritant contact dermatitis and allergic contact dermatitis caused by contact with cosmetics. Many factors can affect the allergenicity of a certain cosmetic product, including the composition, concentration and purity of cosmetic raw materials, the conditions of use of the product and the site, the time of contact with the skin, the frequency of use, and the preservation of the product. If the consumer belongs to the "sensitive skin", cosmetics allergy also has an important impact.
Most of the side effects of cosmetics are irritation reactions, but some patients may have allergic reactions such as cosmetic allergic contact dermatitis. The prevalence of cosmetic allergy in the general population is about 10%, while the actual incidence may be much higher than this, as most patients only experience mild allergic or irritant reactions, which are relieved by discontinuing cosmetics on their own, and are less likely to seek treatment at the hospital. The highest positivity rate was found for preservatives in the cosmetic line, with carzon CG, methylisothiazolinone, and thimerosal all belonging to the preservative group of allergens. Casone CG is a preservative made from a mixture of 1.15% methylchloroisothiazolinone and 0.35% methylisothiazolinone and is mainly found in soaps, shampoos and conditioners, mascara, and skin creams. Cobalt chloride has a high rate of positivity in patients with contact dermatitis. Cobalt chloride is commonly found in colored glass and porcelain, and also in alloys. Formaldehyde is also a common allergen in patients with facial dermatitis.
The use of a brand of cosmetics need to do an allergy test, due to the more sensitive location of the ear root, so the cosmetics will be applied to this location for about an hour without adverse reactions, then you can basically confirm that the cosmetics are not allergic.
First, locate the base of the ear and apply some of the cosmetic product you want to test to the base of the ear. Wait a day or more for the results.
Sensitive skin test may take a little longer than others, so girls who are not sure whether they are sensitive or not can go for a skin test.
And besides behind the ear can be tested for cosmetic allergies, the inner elbow, inner wrist, and small area of skin on the neck can also be used to test for cosmetic allergies. Because these skins are also very sensitive, the test results will also be more accurate.
Note: The cosmetic behind-the-ear test can only test whether you are allergic to the cosmetic, not whether this cosmetic is suitable for your skin type, so you need to pay attention to whether you are suitable for your skin type after determining that you are not allergic to the cosmetic.
Use distilled water or saline to wet a piece of gauze, twisted to half dry, and folded into 4 layers of about 1 square centimeter size, the cosmetics coated in the gauze side, and then applied to the forearm extension or back normal skin, and then covered with 1.5 square centimeters of impermeable cellophane or plastic film, fixed with tape. After 24~48 hours of observation, if the test site is itchy or burning pain, indicating that the cosmetic product is irritating to the skin, then it is a positive reaction, and the test substance should be removed in time and rinsed with water. If the test site does not have any symptoms, it is a negative reaction, indicating that the cosmetic is not irritating to the skin and is safe. If there is simple erythema, itching, it is weakly positive; redness, swelling, pimples is moderate positive; significant redness, swelling, pimples and blisters is strong positive; significant blisters or even necrosis, it is very strong positive. Positive reactions should be washed and treated in a timely manner, and suggest that the cosmetic product should never be used.