Melasma (chloasma)

Melasma is a chronic skin disorder that results in symmetrical, blotchy, brownish facial pigmentation.

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 (dermal melanosis)

Known triggers for melisma include:

1. Sun exposure
2. Pregnancy—often fades a few months after delivery
3. Hormone treatments—OCP, HRT, IUD – common cause of melasma
4. Chemicals cause a phototoxic reaction that triggers melasma
5. Hypothyroidism (low levels of circulating thyroid hormone)

Melasma commonly arises in healthy, non-pregnant adults and persists for decades. Exposure to ultraviolet radiation (UVR) deepens the pigmentation because it activates the melanocytes to produce more melanin.

Tx – General measures

• Discontinue hormonal Rx, avoid offending chemicals
• Sun Protection & make-up

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).
• Azelaic acid cream, lotion or gel can be used long term, and is safe even in pregnancy. This may also sting.
• Kojic acid is often included in formulations, as it binds copper, required by L-DOPA (a cofactor of tyrosinase).
• Ascorbic acid (vitamin C) also acts through copper to inhibit pigment production. It is well tolerated but highly unstable

Other active compounds used for melasma include:

• Topical corticosteroids such as hydrocortisone. These work quickly to fade the colour and reduce the likelihood of contact dermatitis caused by other agents.
• Soybean extract, which is thought to reduce the transfer of pigment from melanocytes to skin cells (keratinocytes) and to inhibit receptors.

Superficial or epidermal pigment can be peeled off. Peeling can also allow tyrosinase inhibitors to penetrate more effectively.

• 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.

The most successful formulation has been a combination of hydroquinone, tretinoin, and moderate potency topical steroid.

What is the outcome of treatment of 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.