Melasma

The cause of melasma is complex. The pigmentation is due to overproduction of melanin by the pigment cells, melanocytes, which is taken up by the keratinocytes (epidermal melanosis) and/or deposited in the dermis (dermalmelanosis, melanophages). There is a genetic predisposition to melasma, with at least one-third of patients reporting other family members to be affected. In most people melasma is a chronic disorder.

Known triggers for melasma include:

• Sun exposure and sun damage—this is the most important avoidable risk factor
• Pregnancy—in affected women, the pigment often fades a few months after delivery
• Hormone treatments— oral contraceptive containing oestrogen and/or progesterone, hormone replacement, intrauterine devices and implants are a factor in about a quarter of affected women
• Certain medications (including new targeted therapies for cancer), scented or deodorant soaps, toiletries and cosmetics—these may cause a phototoxic reaction that triggers melasma, which may then persist long term
• Hypothyroidism (low levels of circulating thyroid hormone)

melasma can be very slow to respond to treatment, especially if it has been present for a long time.

General measures

Discontinue hormonal contraception.
Year-round life-long sun protection. Use broad-spectrum very high protection factor (SPF 50+) sunscreen applied to the whole face every day. It should be reapplied every 2 hours if outdoors during the summer months. Alternatively or as well, use a make-up that contains sunscreen.

Devices used to treat melasma

The ideal treatment for melasma would destroy the pigment, while leaving the cells alone. Unfortunately, this is hard to achieve. Machines can be used to remove epidermal pigmentation but with caution—over-treatment may cause postinflammatory pigmentation. Patients should be pretreated with a tyrosinase inhibitor (see above).

Fractional lasers, Q-switched Nd:YAG lasers and intense pulsed light (IPL) appear to be the most suitable options. Several treatments may be necessary and post-inflammatory hyperpigmentation may complicate recovery.

Carbon dioxide or erbium:YAG resurfacing lasers, pigment lasers (Q-switched ruby and Alexandrite devices) and mechanical dermabrasion and microdermabrasion should be used with caution in the treatment of melasma.

Topical therapy

Tyrosinase inhibitors are the mainstay of treatment. The aim is to prevent new pigment formation by inhibiting formation of melanin by the melanocytes.

• Hydroquinone 2–4% as cream or lotion, applied accurately to pigmented areas at night for 2–4 months. This may cause contact dermatitis (stinging and redness) in 25% of patients. It should not be used in higher concentration or for prolonged courses as it has been associated with ochronosis (a bluish grey discolouration similar to that seen in alkaptonuria).
• Azelaic acid cream, lotion or gel can be applied twice daily long term, and is safe in pregnancy. This may also sting.
• Kojic acid or kojic acid dipalmitate is often included in formulations, as it binds copper, required by L-DOPA (a cofactor of tyrosinase). Kojic acid can cause irritant contact dermatitis and less commonly, allergic contact dermatitis.
• Ascorbic acid (vitamin C) also acts through copper to inhibit pigment production. It is well tolerated but highly unstable, so is usually combined with other agents.
• Methimazole (antithyroid drug) cream has been reported to reduce melanin synthesis and pigmentation in hydroquinone-resistant melasma.
• Superficial or epidermal pigment can be peeled off. Peeling can also allow tyrosinase inhibitors to penetrate more effectively. These must be done carefully as peels may also induce post-inflammatory pigmentation.
• Topical alpha hydroxyacids including glycolic acid and lactic acid, as creams or as repeated superficial chemical peels, remove the surface skin and their low pH inhibits the activity of tyrosinase.
• Topical retinoids, such as tretinoin (a prescription medicine) are effective. Tretinoin can be hard to tolerate and sometimes causes contact dermatitis. Do not use during pregnancy.
• Salicylic acid, a common peeling ingredient in skin creams, can also be used for chemical peels, but it is not very effective in melasma

Results take time and the above measures are rarely completely successful.

Unfortunately, even in those that get a good result from treatment, pigmentation may reappear on exposure to summer sun and/or because of hormonal factors. New topical and oral agents are being studied and offer hope for effective treatments in the future.