At present, there is no uniform definition of cosmetics in the world. According to the current EU cosmetic regulations, cosmetics are substances and preparations that contact with external organs (epidermis, hair, toenails, lips and genitalia), or teeth and oral mucosa in the oral cavity, with the main purpose of cleaning, emitting fragrance, improving appearance, improving body odor or protecting the body to keep it in good condition. The food and Drug Administration (FDA) defines cosmetics as "smear, spread, spray or other methods that can be used in the body. It can clean, beautify, and make attractive or change the appearance." The definition of cosmetics in Japan is: for the purpose of cleaning and beautifying the human body, increasing the charm, changing the appearance, keeping the skin and hair healthy and healthy, the articles smeared, distributed on the body or used by similar methods are the substances that have a mild effect on the human body.

According to China's "Hygienic standard for cosmetics" (2007 Edition), cosmetics are defined as daily chemical industrial products which are spread on any part of human body surface (skin, hair, nails, lips, etc.) by smearing, spraying or other similar methods, so as to achieve the purpose of cleaning, eliminating bad smell, skin care, beauty and decoration. The definition of cosmetics from the use of cosmetics, application site and purpose of three aspects of a more comprehensive summary.

Although the definition of cosmetics varies from country to country, there is no essential difference. At the same time, it should be specially pointed out that the functional parts of cosmetics are the surface of the human body, including the skin surface, hair surface and nail surface. Hyaluronic acid (for subcutaneous injection), whitening needle, botulinum toxin, etc. sold on the market or used by some beauty salons do not belong to the category of cosmetics.