Human complexions are generally classified into six skin types. In uncommon cases, hair may lose all pigmentation early in life. For example, some people are predisposed to premature graying. For these people, their hair may lose all pigmentation by the time they are 20 years old. Normal pigmentation may be altered by genetic defects or by acquired diseases.
External agents can also alter skin color.
For example, lightening agents, carotene or dyes used in tattooing can alter skin color. Hyperpigmentation Hyperpigmentation means an excess of pigment. Freckles tend to be more pronounced in childhood. They are associated with fair hair and skin. Hyperpigmentation is seen in cases of hyperpituitarism and Addison's disease.