The major endogenous pigment in the skin is melanin and tattoo ink the major exogenous pigment. Melanin, unlike other skin tissue chromophores does not have defined absorption peaks; instead increasingly absorbing shorter wavelengths from 1000nm through to the ultraviolet spectrum. Thus, a variety of laser and light wavelengths can be used to target melanin, although none is entirely specific for this chromophore: Many lasers in the wavelength band width of 500-800nm (532nm-KTP, 595nm-PDL, 694nm-Ruby, 755nm-alexandrite) and even the 1064nm QS Yag laser may be used..
The band of wavelength that needs to used depends how superficially the pigment resides. Superficial (epidermal) pigment is encountered in solar lentigines, ephelides, café-au-lait macules and seborrhoeic keratosis and may be selectively targeted with long pulsed as well as Q Switched lasers. Water seeking infrared ablative lasers such as Erbium and CO2 and the non ablative fractional Thulium lasers are all useful in the treatment of widespread pigmentation when the pigment is within reach. Similarly, IPL is an effective “broad brush” approach for many cases of widespread epidermal pigmentation and dyschromias.
However, deep (dermal) pigment is a feature of melanocytic naevi, blue naevi, naevi of Ota/Ito, Hori’s naevus, drug-induced hyperpigmentation requires both long wavelengths to achieve the depth required without superficial absorption and short pulse duration to target pigment specifically and safely without drift to unintended targets. Melasma remains a conundrum for all laser users and will be one of many conditions that will be highlighted as those not well treated by lasers.