Ashy dermatosis, also called erythema dyschromicum perstans, is a skin disorder characterized by gray-blue patches on the skin. Here are three things you need to know about ashy dermatosis.

What are the signs of ashy dermatosis?

Ashy dermatosis usually develops during the first three decades of life. When the condition first develops, it presents as a single, gray-blue, asymptomatic lesion on the trunk of the body. This first lesion is typically between 0.5 and 2 centimeters (0.2 and 0.8 inches), but over time, it can spread to cover the trunk, face, and even the extremities. The only parts of the skin that are spared by ashy dermatosis are the palms of the hands, soles of the feet, nail beds, scalp, and mucous membranes.

What causes ashy dermatosis?

The cause of ashy dermatosis is still unknown. It's suspected to be caused by exposure to ammonium nitrate, a chemical that is found in fertilizer. Whipworms, a type of intestinal parasite, have also been suggested as a possible cause. Researchers also suspect that environmental factors like pollutants may be the cause of this skin condition, though they haven't been able to identify a specific pollutant that may be responsible.

It's more common among women and people with dark skin, according to the Indian Dermatology Online Journal. Most adult patients have Hispanic or South Asian ancestry, but when children develop it, they're usually Caucasian. More research needs to be done to figure out why these groups of people are more likely to develop ashy dermatosis.

Can ashy dermatosis be treated?

Ashy dermatosis doesn't usually go away on its own, so you'll need to see a dermatologist for treatment. A number of medications have been used to treat ashy dermatosis, including Clofazimine. Clofazimine is a drug used to treat leprosy, and you may need to take it for as long as five months to see considerable improvement in your skin color. Dapson, another leprosy drug, can also be used to treat this condition.

If these drugs don't work, medications like antibiotics, antihistamines or corticosteroids can also be tried, though they may not produce satisfactory results. Chemical peels—cosmetic procedures that use chemical solutions to strip away the upper layer of your skin—can also be attempted to treat this condition. The goal of this treatment is that when your upper layer of skin regrows, it will be its normal color, not grey-blue.

If you have grey-blue discoloration on your skin, see a dermatologist right away for treatment.