Dihydroxyacetone: A Review

Dihydroxyacetone (DHA) is a 3-carbon sugar (Figure 1) found in sunless tanning products.¹ It is the only color additive allowed by the Food and Drug Administration (FDA) for external use as a color additive in sunless tanning products (also called sunless tanners).^1,2 In the 1920s, it was first introduced as a sweetener in diabetic diets.³ At the Cincinnati Children’s Hospital in the 1950s, DHA was studied in children with glycogen storage disease who underwent an oral tolerance test with DHA.^4,5 During the oral tolerance test, some children regurgitated DHA and exposed their skin to DHA products.^4,5 These children were found to have darker skin in the areas exposed to regurgitated DHA.^4,5 This led to the recognition of DHA as a sunless tanning agent.⁴ Following a safety review as part of the FDA’s color additive petition process, the first topical sunless tanning product was marketed in 1977.^6,7 Since then, the sunless tanning industry has experienced rapid growth due to public education on the dangers of ultraviolet (UV) radiation on the skin and further development of sunless tanning products.¹ Despite the increased popularity of sunless tanners, research on the safety of these products remains limited. We review the literature on DHA including consumer use, published safety data, current regulations on its use, its potential clinical utility, and its possible photoprotective properties.

When DHA is topically applied, it reacts with amino acids such as glycine, alanine, leucine, and valine¹⁵ to form a brown-colored complex, in a non-enzymatic glycation reaction known as the Maillard reaction, in the stratum corneum to impart a tanned appearance.¹ Sunless tanners are topically applied and typically contain DHA and moisturizers.⁸ Marketed formulations sold commonly contain 3% to 5% DHA and can be applied topically as a cream or lotion at home.^1,8,9 DHA has been used in spray-tan booths and airbrushing products containing DHA by technicians onto consumers, although these are unapproved uses if contact with the color additive is not restricted to external parts of the body.^1,8,9 The degree of the tan is the result of the concentration of the DHA used and the number of applications.¹⁰ Pigmentation is typically observed within 1 hour following DHA application, peaks between 8 to 24 hours, and persists for 5 to 7 days.^3,10 Pigmentation is lost with sloughing of keratinocytes.¹¹ The number of applications and frequency of reapplication required to maintain color depends on anatomic location, with thicker skin sites (eg, arms and legs) requiring less frequent application compared to thinner skin sites (eg, face).¹⁰ Other commonly applied products that sometimes contain DHA are bronzers.⁸ Bronzers, commonly marketed as tinted moisturizers and brush on powders, are often used to describe a variety of products intended to achieve a temporary tanned appearance.^1,2 Bronzers are temporary and do fade with time and are removed with the use of soap and water.^1,2 Individuals can apply DHA products at home or pay professionals at salons and spas to apply the product topically.¹ Prior to application, marketing literature recommends that consumers