1, photosensitivity: when the light changes, it no longer plays a role, such as unstable vitamins such as VC.
2. Hydrocarbons: including aromatic compounds, which will react chemically when exposed to light, and their products will harm the skin and cause pigmentation. Such as various essential oils.
It is found that ultraviolet rays in sunlight can stimulate the skin to produce a large number of oxidative free radicals, destroy skin cells and tissues, accelerate the oxidation reaction of melanin production, make the skin dull, rough and inelastic, and reduce the skin's resistance.
Extended data
Common photosensitive substances-cosmetics
Common photosensitive substances that cause mild contact dermatitis are cosmetics, such as spices (bergamot oil, lemon oil, sandalwood oil) and impure vaseline. Dyes, such as Lavnol, methylene blue, eosin, etc. ; Drugs, such as sulfanilamide, topical antipruritic drugs such as benzocaine, etc. Coumarins, such as methoxysarin, trimethoprim and angelica dahurica; Optical brightener.
Tip: When you choose brand products, you are generally not vulnerable to this kind of injury. If the skin is light-sensitive, that is, despite the sunscreen care, the forehead, cheeks and nose are still prone to allergic reactions, then you must pay special attention to whether these substances appear around you.
Baidu encyclopedia-photosensitive substances
Baidu encyclopedia-light whitening