What is skin whitening and why do it?
Skin whitening is a practice in which the production of melanin is inhibited, making the skin brighter. It is particularly popular in Africa and Asia, where a fair skin is culturally regarded and brings certain social benefits. Mainly a worldview aspect in Asia, the people in Africa hope for higher chances of marriage and work.  But it is also practiced in many other countries. Here are mainly medically treated pigmentary disorders and diseases. In addition, the complexion is cosmetically balanced. 
What is used and how does it work?
In Japan, a long time was looking for possible substances, where mainly kojic acid and rucinol are used. The only whitening substances approved in Germany are mixtures of hydroquinone, tretinoin and hydrocortisone. They mainly work by influencing melanin synthesis in the body.  Melanin is a pigment in the body that gives the dark color of the skin. Likewise, melanin protects us from UV radiation. Side effects of these bleaches are:
Hydroquinone: classified as a carcinogen under REACH (ECHA Evaluation - Item 7.9.5)
Tretinoin: Causally causes skin irritation
Hydrocortisone: is a body's own stress hormone, which is involved in the metabolism. Prolonged exposure may cause skin thinning, acne or dermatitis (primarily around the mouth).
In some parts of Asia and Africa, one often resorts to more dangerous means, e.g. Mercury. 
Are there alternatives ?
As alternatives come substances in question, which act as a light tyrosinase inhibitor. These prevent tyrosine from producing melanin. They are found in synthetic as well as natural sources. e.g. Kojic acid, vitamin C, ortho-vanillin or various ingredients of licorice root extract.  In addition, alpha-hydroxycarboxylic acids can be used to remove old, darker skin layers (the so-called fruit acid peeling). 
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