In cosmetics, allergens can be found in emulsifiers, solvents, dyes,fragrances and preservatives.These allergens have the potential to cause allergic contact dermatitis (ACD) after one or repetitive skin exposure.One of the popular practices to control the induction threshold of sensitization (type Ⅳ) is using the Quantitative Risk Assessment (QRA) approach.However, with increasing evidences showing there is cocktail effect (synergy or additive) under exposure of mixed contact allergens, this method that applicable to the risk control of singular allergen may need to be adjusted when dealing with mixed allergens in formula.