INTRODUCTION
Despite growing awareness of the harmful effects of ultraviolet induced tanning on photocarinogenesis and photoaging of the skin, the tanned look remains popular among Americans. Tanned skin can cause interference and complications with laser treatment, such as hypo- and hyperpigmentation, decreased treatment efficacy, and scarring. Dihydroxyacetone (DHA), commonly found in sunless tanning lotions and spray on tans, is the only FDA approved color additive for use as a tanning agent. It binds in the stratum corneum and forms brown-black compounds called melanoids, giving the appearance of a tan.1,2 In short, DHA induces a formation of brown color complexes through glycosylation of amines or amino groups in skin proteins. The process is known as the Maillard reaction and involves the formation of free radicals. The depth of color depends on the thickness of the stratum corneum. The brown color complexes are water and soap resistant and pig- ment loss occur through sloughing of the stratum corneum. Reflectance spectrophotometers have been used to estimate the absorption spectrum of the various chromophores in the skin, which can predict their interaction with the ever growing number of lasers used in dermatology. We performed reflectance spectrophotometry on non-sun exposed skin after seven days’ application of DHA to quantify the absorption spectrum of skin treated with daily application of DHA, using the other arm as a control.
CASE REPORT
Commercially available DHA 5% cream (L’Oreal Paris Sublime Bronze, Medium) was applied to the underarm skin once daily for 7 days. The seven-day application routine was based on instructions from the manufacturer for optimal “tanning”. Clini- cally signi cant staining of the skin was noted. Re ectance spectrophotometry (HR2000+, Ocean Optics Inc, Dunedin, FL) was performed on the stained skin and on the matching skin on the other side for use as a control. Estimated absorption was derived and plotting utilizing the re ectance sprectrophotom- etry data. Increased absorption was demonstrated in a band from 300-700 nm (Figure 1).
DISCUSSION
DHA-treated skin demonstrates decreased reflectance in the 300-700 nm range compared with untanned skin. In comparing the DHA induced changes in reflectance spectra with changes due to native melanins in the epidermis (ie, natural tanning or variations in Fitzpatrick skin type), the DHA induced changes are more focal at 480 and 630 nm. Melanin, on the other hand, shows an almost linear decay in absorption across the 300-700 nm band. Our findings are consistent with a prior study observing the absorption spectrum of byproducts of DHA application.3 From a practical standpoint lasers utilizing those wavelengths, in particular potassium titanyl phosphate (KTP, 532 nm), pulsed dye (PDL, 585-595 nm), and intense pulsed light (IPL, 400-1200 nm) should be used with caution. Due to the superficial nature of the DHA deposition, most likely side effects would be very superficial epidermal crusting and decreased efficacy of treatment. As the reported duration of a DHA induced tan is 5-7 days,1 we would recommend waiting 7-10 days after application of DHA to allow for shedding of the stratum corneum prior to using these lasers in practice.
