Although the laser energy has been shown to be an effective means of reducing hair growth on the face, its efficacy is limited by the requirement for the heat-absorbing chro- mophore, melanin. Thus, facial hair that is not darkly pigmented is less susceptible than darker hair, resulting in uneven efficacy within an individual and variability across the population. For hair follicles with very low pigmentation such as in blonde, gray, or extremely light hair, the laser system is generally ineffective. Two approaches have been explored to treat lightly-pigmented or unpigmented hair; one is related to targeting preformed melanin to hair follicles using liposomal preparations, and the other is related to combining a melanin responsive Laser/IPL with a photo-thermal energy that does not require melanin as chromophore, such as a radiofrequency (RF) source.
Sadick et al. studied the combination of IPL/RF technology in 40 patients with varied hair colors [41]. There were at least 11 subjects with blonde, red, and white color hair in the study. The face was the most common site, treated with ten enrolled subjects. Four treatments were administered over a period of 9-12 months at 8-12 week intervals. The fluence applied for IPL ranged from 15-26 J/cm2 depending on the patient’s skin and hair color, and the RF energy range was 10-20 J/cm2 depending on the treatment site. The average clearance recorded at 18 months was 80-85% for brown and black hair and 40, 60, and 60% for white, red, and blonde hair. The average clearance on the face was 65%. The treatments were well-tolerated by the patients, with no significant dermal adverse events. The study provides evidence that unpigmented or lighter hair can be effectively treated with the IPL/RF combination.
Although there are several literature reports on the targeted delivery of macromolecules to hair follicle, its utility in man is yet to be proven. Melanin is a large polymer molecule which is simply too large to penetrate the skin using conventional topical formulation. Attempts have been made to enhance melanin penetration by encapsulating it in a liposomal preparation. To enhance the lasers’ efficacy for gray and blonde hair, not only does melanin need to penetrate the skin surface, it also needs to be delivered in sufficient amounts to the base of the hair follicle, which has been challenging to achieve. A recent study by Sand et al. [42] looked at the effect of topical preparation of encapsulated melanin on hair growth inhibition of white/gray hair by laser (three cycles of 800 nm diode laser at 28-40 J/cm). Hair counts were taken eight weeks after each laser treatment and six months after the last treatment. A statistically significant 14% reduction was observed with the melanin group versus 10% with placebo. These findings were not considered to be clinically significant.