Niacinamide is a derivative of vitamin B3, which can promote skin metabolism and has the effect of whitening, anti-aging, pore shrinking, oil control and acne removal. The use of niacinamide substances can accelerate the shedding of melanin cells in the skin and promote skin metabolism. Although niacinamide is now widely used in skin care and makeup products, there are certain side effects, as follows: 1, skin allergies: for some people with sensitive skin, niacinamide itself has a certain degree of irritation, in the case of insufficient skin tolerance, the blind use of products containing niacinamide may cause skin redness, swelling, pain, itching, peeling, and even dizziness and Nausea and other symptoms; 2, accelerate hair growth: because niacinamide has the effect of promoting skin metabolism, some beauty seekers in the use of such products, niacinamide stimulates the metabolic rate of the epidermis, which eventually leads to accelerated hair growth, making the problem of facial hair more serious. Therefore, when using niacinamide products, candidates should first perform a skin allergy test behind the ear to avoid adverse reactions.