The colour of skin is due to a natural pigment (melanin) and the way keratinocytes at the surface of the epidermis reflect light.

Melanin

Melanin is synthesized in special cells called melanocytes and located in the deeper layer of the epidermis. The pigment is excreted in the form of granules (melanosomes) which are distributed into keratinocytes. These granules are progressively disintegrated as the keratinocyte layers migrate upwards. In white skin, there no more melanin in the is dead cells of the upper layers unlike in black skin, characterized by a greater of melanin. The production of melanin is stimulated by exposure to UV rays.

KERATINOCYTES

Dead cells at the surface of the epidermis may rend a dull aspect of the skin . This is why a mild exfoliation allows a clearer complexion. It is particularly important in black or spotted skin which is characterised by a thicer stratum corneum.

ABOUT WHITENING SUBSTANCES

People have been using lightening products either to obtain an overall fairer and whiter complexion or to tone down ageing and sun spot which are due to localised over production of melanin. The skin whitening properties of hydroquinone were accidentallydiscovered in the USA during World War II. Coloured tanners wearing rubber gloves complained about having discoloured areas on hands and forearms. After all the possible pathological hypotesis were eliminated, a study of every chemical element involved incriminated on intermediary agent used in rubber synthesis: hydroquinone. The idea of using this molecule to voluntarily depigment skin was quickly picked up as at that time, the only depigmenting products being dangerous mercurial and peroxygenated derivatives. Further research determined the maximum dosage above which the effect is irreversible. Furthermore, irritation and sensitisation appeared. Hydroquinone usage level was thus limited to 5% and then 2% at least in France.Not only does the use of hydroquinone encounters legal problem but has also created troubles to the formulator due to its high instability.

A NEW COCKTAIL OF DIFFERENT SUBSTANCES