Sunlight is one of the major factors that influences the increased
functional state of melanocytes in melasma. Its high incidence in
tropical areas, and the recurrence of the hyperpigmentation after
sunlight exposure provide clinical evidence of the role of solar
radiation in the pathogenesis of melasma.
Because the wavelength that darken pigment extend from ultraviolet
(290-40Onm) into the visible spectrum, protection of the broadest range
should be recommended.
Sunscreens are agents that physically or chemically block the
penetration of UV light into the skin. Sunscreens usually contain more
than one agent to provide greater protection over the range of UVL
wavelengths. Products that provide protection in both UVB and UVA are
called full or broad spectrum sunscreens.
When used as directed, a sunscreen rated SPF 15 is usually adequate
for most skin types. Sunscreens with an SPF greater than 15 may be more
protective but are more expensive. They may also increase the
possibility of irritation and contact allergy because they contain
multiple sunscreen agents in higher concentrations.
Adverse effects to sunscreens are on the whole uncommon. Chemical
sunscreen agents, particularly derivatives of PABA, benzophenones,
dibenzoyimethanes and anthranilates, can occasionally cause both
allergic & photo-allergic contact dermatitis. In addition, PABA
containing preparations can stain clothing yellow and cause stinging of