Your doctor will diagnose the condition through a physical examination and a medical history. A thyroid test may be conducted to rule out thyroid disease. Examinations are often done using a Wood’s lamp or light, which shines ultraviolet light onto your skin. This will help your doctor identify whether the affected melanin is in the dermis or epidermis. (However, this type of light cannot be used accurately on people with dark brown skin.) Your doctor may also ask if you experienced any inflammation before the dark patches appeared, have been exposed to chemicals, or have been taking any medications that might cause pigment deposition.
Your doctor will also want to rule out other conditions that can cause the patches, such as menopausal changes, certain types of ovarian tumours and disorders such as Addison’s disease.
Melasma cannot be cured, and many cases require no treatment at all. For example, the melasma associated with pregnancy usually fades slowly after delivery; similarly, dark patches will fade eventually after discontinuation of oral contraceptive use. It will likely recur upon subsequent pregnancies or when restarting use of the contraceptive.
Cases of melasma where the melanin is in the deeper layer (dermis) are slower to resolve than cases in which melanin is restricted to the epidermis, as pigment deposited in the skin’s deeper layers cannot be physically removed. Treatment of dermal melasma aims to prevent the melanin in the dermal layer from being replenished. This results in very slow fading of the pigmented areas. In all cases, strict avoidance of sunlight is crucial to successfully resolving melasma and preventing resistant cases or recurrences.
Treatments for melasma include:
Topical Depigmenting Agents
- Hydroquinone (HQ) is a chemical that interferes with the process that melanocytes use for producing melanin. Formulations with higher amounts of HQ are more effective than those with lower amounts; however, adverse side effects increase with drug concentration. Side effects include skin irritation, sensitivity to light, and hyperpigmentation (darkening of the skin), some of which may be irreversible. Tretinoin (trans-retinoic-acid) is thought to increase the turnover of skin cells in the epidermis, which limits the transfer of melanin to the skin. Tretinoin is often used in combination with HQ as response is slow when tretinoin is used alone. Its side effects include skin irritation, temporary sensitivity to light and hyperpigmentation.
- Azelaic acid reduces melanocyte function. Unlike HQ, azelaic acid seems to target only hyperactive melanocytes. Normal melanocytes in light skin will not be affected. The primary adverse effect is skin irritation.
- Other depigmenting agents under study include 4-N-butylresorcinol, phenolic-thioether, 4-isopropylcatechol, kojic acid, and ascorbic acid.
Chemical and surgical peels
Chemical peels, microdermabrasion, and laser surgery have all been used to remove the layer of skin with the malfunctioning melanocytes. Results are obtained quickly but are unpredictable and may be temporary, as the melanocytes on the new skin may also malfunction. Such procedures can also irritate the skin, which can worsen melasma. Some physicians combine mild exfoliation with topical depigmenting agents. A number of studies have found this to be safe and effective.