An analysis of a 10-year survey of allergy rates to commonly used preservatives conducted at 16 research centers in 11 countries showed that formaldehyde and methylisothiazolinone allergy rates have been at high levels. Although formaldehyde is rarely used directly as a cosmetic preservative, many other preservatives in cosmetics can release formaldehyde after use, commonly imidazolidinyl urea, bis-imidazolidinyl urea, quaternary ammonium salt-15, DMDM acetonyl urea, urotropin, 2-bromo-2-nitropropane-1,3-diol, 5-bromo-5-nitro-1,3-dioxane. In China and the European Union cosmetics regulations, the free formaldehyde content in cosmetics shall not exceed 0.2%, however, many literature reports that formaldehyde causes allergy or dermatitis threshold concentration required is much lower than this, 0.003% and 0.025% can be caused.
2, fragrances: about 20% -30% of the cosmetics dermatitis and allergens. Fragrance ingredients can cause dermatitis or photosensitive contact dermatitis in the application site, which is why in recent years a variety of main sensitive muscle use of skincare products do not add fragrance.
The common allergens of fragrances are: fragrance mixtures, hydroxy-isohexyl-3-cyclohexenecarboxaldehyde, Peru balsam, and tea tree oil.
3, surfactants: about 15% of allergens. Surfactants on human skin, eyes, hair, especially on the skin, eye irritation is a rather difficult to define the concept, as of now there is still no uniform standard. Surfactant according to the structure, the different varieties, the intensity of its irritation has obvious differences, the same chemical structure, manufacturers, process routes and raw materials taken by different will have a big difference. Surfactant irritation or sensitization of the skin or mucous membranes is mainly caused by the following three factors.
① Dissolution: refers to the degree of dissolution of surfactants on the skin itself moisturizing ingredients, intercellular lipids and free amino acids and fats in the stratum corneum. Excessive dissolution of these ingredients will cause damage to the surface layer of the skin, the skin's ability to reduce water retention, causing the cells into the dermal flakes off, resulting in skin tightness, stinging or dry feeling.
② penetration: refers to the ability of surfactant transdermal penetration, this effect is considered to be one of the causes of various inflammatory skin. Surfactant infiltration changes the original structural state of the skin and the phase solubility between neighboring molecules, resulting in skin irritation or even cause allergic reactions, so that the skin appears on the erythema and edema phenomenon. Surfactant irritation of the skin mucosa to the most cationic type, followed by anionic type, non-ionic and amphoteric type minimum.
③ Reactivity: refers to the adsorption of surfactants on proteins, resulting in protein denaturation and change the pH conditions of the skin and other effects. Tests have shown that nonionic surfactants are less reactive, and anionic surfactants are more reactive.
Surfactants common sources of sensitization are: amercholL101, cetyl/stearyl alcohol, cocamidopropyl betaine, lanolin alcohol
4, hair dyes: eye irritation is more pronounced than the skin, especially p-phenylenediamine. Samples that are not irritating to the skin cannot exclude irritation to the eyes and vice versa.
5, other allergens: in addition to the sunscreen, antioxidants, antimicrobial agents in cosmetics are skin sensitivity and stimulation of common allergens.
Common allergens are: benzophenone-3, 4-aminobenzoic acid.