Coloring the skin with dihydroxyacetone to create an artificial tan was discovered serendipitously in the 1950s by Eva Wittgenstein, whose patients were taking DHA orally. She observed that when patients regurgitated the DHA, pigmented spots remained on the skin (Science 1960;132:894-5).
The change in pigmentation results from the interaction of DHA with amino acids in the stratum corneum (Br. J. Dermatol. 2003;149:332-40).
Although the first product brought to market to exploit this new knowledge in 1959 met with initial success, it fell into disuse because of the poor cosmetic results (J. Am. Acad. Dermatol. 2003;49:1096-106; South. Med. J. 2005;98:1192-5).
Public awareness of sunless tanning has grown in recent years, however, and has been met with formulations that afford a much improved cosmetic performance, with DHA remaining as the main active ingredient in sunless-tanning agents (South. Med. J. 2005;98:1192-5; Am. J. Clin. Dermatol. 2002;3:317-8).
This column will briefly review the role of sunless-tanning lotions and sprays in dermatology, and will try to place recommendations to patients about sunless tanners in the context of sunscreens and tanning attitudes.
Sunless tanners have been used, with varying degrees of popularity, for 50 years; recent evidence suggests that the use of these products has increased in recent years. A long track record of usage and research indicates that sunless-tanning compounds are safe (J. Environ. Pathol. Toxicol. Oncol. 1984;5:349-51; Am. J. Clin. Dermatol. 2002;3:317-8; South. Med. J. 2005;98:1192-5; J. Am. Acad. Dermatol. 2007;56:387-90.) However, there is some debate as to whether the use of these products renders users more inclined to stay in the sun longer. Also, ongoing research has raised some safety issues regarding DHA.
Chemical Protection
In 2004, Petersen et al. investigated the effects of DHA on cell survival and proliferation of a human keratinocyte cell line, HaCaT. Significant genotoxic activity was identified in these cultured cells, as researchers noted dose- and time-dependent morphologic alterations as well as cytoplasmic budding and cell detachment in DHA-treated cells, and apoptosis and marked declines in proliferation 1 day after DHA exposure. Interestingly, the development of DNA strand breaks was prevented via preincubation with antioxidants. The authors suggested that their findings raised concerns about the long-term use of treating the skin with DHA-containing formulations (Mutat. Res. 2004;560:173-86).
A small study by Faurschou et al. showed that DHA provided human skin with modest UVB protection, with a 5% DHA cream applied three times or a 20% DHA cream applied once yielding an effect similar to an SPF 1.6. They acknowledged that most commercial DHA products contain 3%-5% DHA and offer scant protection. A potential advantage of sunless tanners, if they offer protection, suggested the authors, would be that no spots would be left unattended since such gaps would be conspicuous for lack of browning (Arch. Dermatol. 2004;140:886-7).
Howe, Reed, and Dellavalle contended that DHA in self-tanning agents provided enough UVA protection to warrant use as an adjunct to daily sunscreen use for broad-band protection (J. Am. Acad. Dermatol. 2008;58:894). The researchers referenced a 1975 study in which 3% DHA augmented sunlight tolerance among five patients with UVA-sensitive dermatoses (Dermatologica 1975;150:346-51; J. Am. Acad. Dermatol. 2008;58:894).
In 2009, Choquenet et al. assessed the sun protection potency of self-tanners and foundations using an in vitro method to identify indicators such as sun protection factor (SPF), UVA protection factor (PF-UVA), and UVB/UVA ratio. Using seven amino acids in the corneal cells of the epidermis, the investigators identified SPFs virtually equivalent to zero (approximately SPF 2). Conversely, they found foundations to exhibit satisfactory photostability and a non-negligible SPF, noting that such products are safe given their typically once-daily application (J. Dermatol. 2009;36:587-91).
Attitudes and Behavior
Users of sunless-tanning products were found, in a survey of 2,005 randomly selected South Australian adults published in 2001, to be more likely to use sunscreen but less likely to wear a hat or other sun-protective clothing. Sunburns were also linked to the use of sunless tanners in this study (Med. J. Aust. 2001;174:75-8; J. Am. Acad. Dermatol. 2007;56:387-90).
In 2005, Mahler et al. conducted a randomized, controlled trial with 1-month follow-up of 146 Southern California college students to study the impact of UV photoaging photographs and data on the sun protection plans and behaviors of young adults, and whether sunless-tanning lotion might play a role in sun-protective behavior. Of the 146 volunteers, 91.1% completed the "surprise" 1-month follow-up. The intervention consisted of volunteers being shown a UV facial photo and short video illustrating the etiology and results of photoaging. The investigators found that the UV photographic intervention was successful insofar as significantly better sun protection strategies and behaviors were employed by the test group, compared with controls. In addition, they noted that those who used sunless-tanning lotion were more likely to exhibit extensive sun-protective behavior, compared with individuals who received the intervention alone. The authors suggested that such interventions represented a cost-effective approach that might yield behaviors with long-term health benefits in the form of a lower incidence of skin cancer (Arch. Dermatol. 2005;141:373-80).