Chloasma (pour les professionnels)

Melasma (for professionals)

• Melasma is a very cumbersome condition especially in pigmented skin. It is important to note that only superficial located pigment can improve, not the pigment located deeper in the dermis. Examination with Wood’s lamp (360nm, blue light) is a plus (note that it may be less reliable in phototypes IV and above because the pigment is also invariably seen as being dermal).
• Creams act by four mechanisms:

• by killing the melanocyte:
  • phenolic substances such as hydroquinone, methoxyphenol and monobenzone
  • resorcinol

• by inhibiting melanin production:
  • peroxidase inhibitor methimazole= is a noncytotoxic inhibitor of melanin production
  • ebselen
  • tyrosinase inhibitor (kojic acid, azelaic acid, arbutin, glabridin: less effective on human skin that in vitro studies may suggest
• by inhibiting the transfer of melanosomes to keratinocytes:
  • soy bean extracts
  • ebselen
• by increasing keratinocyte turnover (shedding of dead cells)
  • retinol
  • retinaldehyde
  • retinoic acid

• before beginning treatment it is useful to determine the depth where the pigment is located:
  • epidermal: easier to achieve good results.
  • dermal: more challenging to achieve results.
  • mixed: more effective results on epidermal pigment.

Treating melasma

• As first line treatment:

• Hydroquinone :
  • contrary to widespread belief in the 60 years of use of this topical cream:
    • Side effects are allergic contact dermatitis in 5% of cases. Ochronosis remains a rarity in reality and is more likely if concentration is more than 10%, if use is long-term and if skin phototype is IV or more.
    • No skin cancer has ever been reported (Squamous Cell Carcinoma, Basal Cell Carcinoma, Malignant Melanoma). Amusingly serious studies (McGregor D. Hydroquinone: an evaluation of the human risks from its carcinogenic and mutagenic properties. Crit Rev Toxicol.  2007;37(10):887-914.) have even showed that the risk of cancer is lower in workers exposed to hydroquinone dust.

• Retinoids
  • Retinaldehyde has been shown to be twice as effective in depigmentation as retinïc acid but with a less irritating side-effect.

• PRACTICALLY speaking the treatment is done in two phases:
  • Intensive phase
    • duration: 3 months
    • Hydroquinone 3-5% combined with ascorbic acid 3-5% to apply every other day. Note that the association is only stable about three months.
    • Retinaldehyde 0.05% to apply ever other day.
  • Maintenance phase
    • Hydroquinone to apply once a week
    • Retinaldehyde 0.05% to apply every other day.
  • In both phases, use of a suncreen cream is necessary
  • It is important to apply the cream on the whole area where the skin lesion is and not on the lesion itself because a hypopigmented halo can form (except in skin phototypes I and II).

• As second line treatment
  • If pigmentation returns after having excluded a side effect like ochronosis, it is then important to give a non-phenolic topical
  • TIP: How to decide if a depigmenting cream is effective?
  • • Usually, studies are done at three levels:
      • in vitro: Cultured melanocytes where it is easiest to make pigment vanish
      • in vivo in the animal: the cream is usually tried on hairless mice and if a result is seen it is done…
      • …in vivo in the human being where it would be the most useful that a cream worked.
  • • This stepwise approach guaranties that a cream is safe, but also more effective. Indeed protocols in Universities and academic institutions require ethically a stepwise approach to using a topical agent. To compare this with a pharmaceutical product, the Food and Drug Administration (FDA) requires that a medication is safe and effective through reasearch done at these three levels.
    • On a practical point of view, it is wise to check if studies on a depigmenting agent are done at the three levels of if a cream showing only an  in vitro depigmenting effect has directly been commercialized after being shown to be safe in humans.

• • Existing depigmenting creams on the market (non complete list)
    • New
      • deoxyarbutin
      • nicotinamide
      • methimazole
      • soybean extracts
    • Old
      • Hydroquinone
      • azelaic acid: studies  done neither in the animal, nor in the human being
      • kojic acid: studies done in vitro only
      • arbutin: studies done in vitro only

• As third line treamtent
  • For temporary improvement: alpha-hydroxy acid peels (30-70%)
  • If topicals fail to be effective , IPL and Pigment lasers (NDYAG 1064) may me tried, but only performed by a medical doctor with knowledge of skin conditions as there is a risk the colour could get worse.
  • All treatments must be accompanied by a sunscreen of UVB AND UVA of SPF of 30).
  • At last resort, camouflage make can achieve good cosmetic results.

   

This advice is for informational purposes  only and does not replace therapeutic judgement done by a skin doctor.