Skin color is influenced by a person’s genetic heritage as well as environmental factors.  It is determined by the amount of pigment or melanin that is produced in the skin.  The cells manufacturing this pigment are called melanocytes.  These cells are found throughout the upper layers of the skin.  Natural pigment is nature’s way of protecting the skin from ultraviolet light.  A suntan is actually sun damage and does not provide sun protection. 

Uneven pigmentation of the skin may be a natural occurrence or related to ultraviolet light, infection, hormones, drugs, acne or topical chemicals applied to the skin.  There are also skin diseases and genetic abnormalities that can cause hyperpigmentation.  Common causes of hyperpigmentation include sunspots, freckles, “acne spots” and melasma (pregnancy mask). 

Melasma is a common condition seen in women, related to hormones (estrogen) and sun exposure.  This condition is frequently exacerbated during pregnancy, at menopause, and with the use of oral contraceptives.  The skin darkens in patches of tan to brown, primarily on the sun-exposed areas such as the face, neck and arms.  Most sun exposure throughout the day is brief but cumulative. Consequently, brief exposures without sunscreen can cause dramatic changes in skin pigmentation.   

Sunspots, medically called lentigos, and commonly referred to as liver spots, are a product of sun exposure.  This exposure is cumulative and not directly related to sunburn on a specific day.  Sunspots result from the increased production of melanin as a consequence of long -standing sun exposure.  The most common areas involved are the face, neck, upper chest and arms. 

Freckles, medically called ephelides, develop in fair-skinned individuals as a result of sun exposure.  This is the skin’s protective measure against the harmful effects of ultraviolet light. Freckles are predominantly seen on sun-exposed surfaces and will fade when the skin is protected from ultraviolet light. 

Medications are a frequent cause of sudden skin pigmentation.  Most of the pigmentation is seen in sun-exposed areas suggesting an interaction between ultraviolet light and the ingested medication.  Some known medications that can cause skin pigmentation include anti-malarial medications, anti-seizure medications, and minocycline. Ingestion of metal preparations that contain mercury, silver, bismuth, arsenic, lead or gold can also contribute to hyperpigmentation.  Most of the time, a relationship is established between drug ingestion and darkening or irritation of the skin. 

Finally, post-inflammatory skin darkening is a common occurrence after irritation or injury to the skin.  It is more prominent in dark-skin, however, it is also seen in lighter-skin individuals.   After irritation or injury to the skin, the pigment cells (melanocytes) deposit pigment in both the upper and lower layers of the skin.  This is a condition that usually clears with time, although it can last for months to years.  Immediate treatment is important, as this will help determine the outcome and ultimate appearance of the area. 

Recommendations:

First, identify the areas involved, the sequence of pigmentation and the extent of involvement.  If you can identify a source, such as over sun exposure or ingestion of a medication, do your best to decrease or eliminate that source.  

Once the skin is sensitized, the melanocytes are hypersensitive and will repigment readily if restimulated.  It is essential to protect yourself from sun exposure at all times as sun aggravates all of the above conditions.  Skin darkening is treated with bleaching agents such as hydroquinones and mild acids such as glycolic, kojic and retinoic acid.  The hydroquinones should be tried first with application twice daily.  If improvement is slow, topical acids such as glycolic or kojic can also be applied over the hydroquinone twice daily. 

Hydroxy acid peels exfoliate and help lighten the skin. These peels are usually done at home once or twice a week.  It is essential that sun protection be used with at least SPF 15 or greater.  Sun protection should be applied every three to four hours regardless of planned outside activity.  Sunlight is strongest between the hours of 10:00 a.m. and 3:00 p.m.  It is important to remember that sunlight passes through glass and exposure accumulates during the course of the entire day.