If there are more than three preservatives in skin care products, you can't use them.

Three preservatives that must not be used in skin care products are as follows:

1. Casson preservatives: methyl isothiazolinone (MIT) and methyl chloroisothiazolinone (MCI), which are easy to be sensitized and easily lead to irritating dermatitis after long-term use.

2. Formaldehyde-releasing substances: As long as you see the word urea, such as bis (hydroxymethyl) imidazolidinyl urea, this kind of preservative will cause dermatitis, so pregnant women and sensitive muscles should use it with caution.

3. Long-chain nipagin esters, such as butyl hydroxybenzoate and propyl 4-hydroxybenzoate, are easy to be sensitized after long-term use, so be careful with sensitive muscles. Methyl hydroxybenzoate and ethyl hydroxybenzoate are short-chain nipagin esters, so there is no big problem, so don't worry.

Harm of preservatives:

A variety of preservatives will accelerate skin aging. Preservatives in skin care products can't be absorbed and metabolized by the human body, and deposition on the skin will accelerate skin aging. Moreover, preservatives will also accelerate the deposition of pigments on the skin, making the skin more and more dull and prone to allergic dermatitis. Preservatives also increase the possibility of abnormal skin hyperplasia.