The Dark Side of Self Tanner
Sunless tanning agents have been popular since the 1950s and are only growing in popularity as the dangers surrounding natural tanning come to light. Used to maintain that “sun kissed glow” year-round, self-tanning lotions are often used when tanning in the sun is not an option or the dangers of UV exposure want to be avoided. While sunless tanning is very popular in the winter months, there are those that use it in the summer as a way to build upon the natural tan they get from the sun. The sunless tanning industry has experienced rapid growth recently with an increase in public awareness of the dangers of UV radiation. While this option is often portrayed as the safer option due to the ability to avoid UV exposure, this alternative is more harmful than people think. This is because of the safety concerns that surround the main ingredient in these products, dihydroxyacetone (DHA).
What is Dihydroxyacetone?
Dihydroxyacetone (DHA) is a 3-carbon sugar that is the main browning agent used in sunless tanners and the only agent that is FDA approved. Originally introduced in 1920 as a sweetener additive for diabetic diets, it was found that when patients would drop some on their skin it would stain the exposed area brown. Researchers saw the potential in this and in 1977 DHA was repurposed and the first sunless tanner featuring DHA entered the market. Since its initial release, the popularity and use of sunless tanners has skyrocketed. Alarmingly however, what is known about the effects of DHA remains limited and research done by the FDA on the safety of this product is not as comprehensive as the public widely believes. Despite this, DHA is approved for external use in topical sunless tanning lotions in concentrations of up to 15 percent.
How Does DHA Work?
When DHA is applied to the skin, a non-enzymatic glycation chemical reaction known as the Maillard reaction occurs. DHA reacts with the amino acids in the skin cells causing them to be stained a brown-tan color. This is because a byproduct of the Maillard reaction is brown polymers also called melanoidins. The concentration of DHA in the product as well as the number of applications is the main determinant in how dark the tan will become. Melanoidin production typically occurs between one to twenty-four hours with peak pigmentation of the skin occurring within this time frame. The tan produced for these lotions is only temporary and will last about five to seven days and fade as the keratinocytes (the outermost layer of the skin) begin to shed. What this means is that people who want to maintain that tan color will frequently apply multiple layers, constantly exposing their skin cells to DHA.
What is the problem with DHA?
Allergies
An issue that some face when using products containing DHA is allergic reactions and skin irritations. There are a number of different reasons that a person’s skin can react to DHA such as skin type, skin condition, and the amount and composition of the chemicals in the product. While this allergic reaction can happen to anyone, those who have sensitive skin or skin conditions such as eczema and psoriasis are more prone to a DHA allergy. Symptoms of a DHA allergy include hives on the skin, red, swollen, or painful skin at the site of exposure, or rashes on or around the area of application. Prior to using sunless tanners or products containing DHA, it is recommended to do a patch test of the product on the skin in order to ensure that it will not cause an allergic reaction. To do this, apply a small amount of the product to an area of the skin and leave on for approximately twenty-four hours. During this time monitor the area for any reactions.
DNA Damaging Effects
In recent years, concern about the effects exposure to DHA has on skin cells has grown. Recent studies have begun to highlight what happens when sunless tanners are applied to the skin as DHA is rapidly absorbed into skin cells. As discussed, when DHA is applied onto the skin, it reacts with skin cells in a Maillard Reaction. The products of this reaction are advanced glycation end products (AGEs) with reactive oxygen species (ROS) formed as byproducts. AGEs are the stable brown molecules that are produced when the sugar reacts with the amino groups in the keratinocytes. A buildup of AGEs is often linked to skin problems such as discoloration, reduced wound healing times, a reduction in skin elasticity, deeper wrinkles, and accelerated aging. Oxidative stress is associated with higher levels of AGEs making the cell more susceptible to DNA damage. While it was known that the DHA reacts with the amino groups in proteins, scientists decided to research this compound further when it was theorized that DHA might also react with the free amino groups in DNA as well. One study investigated the effects of DHA application on keratinocyte survival and proliferation. What they found is an increase in apoptosis of treated cells due to a cell-cycle arrest potentially from higher levels of DNA damage in the cells exposed to DHA. Similarly, another study found that higher doses of DHA resulted in cytotoxic and genotoxic response in keratinocytes. What these studies and similar studies demonstrate is that there is a correlation between DHA exposure, DNA damage and cell death. This is evidence that these UV alternatives may not necessarily be safe.
What Does this all Mean?
While sunless tanners are an alternative to tanning via UV, they come with their own risks. DNA damage, premature aging, and dermatological conditions may be only a small subset of potential deleterious endpoints associated with DHA exposure, with more research needed to determine the full spectrum of effect on the skin.
Furthermore, the effects of long-term exposure are still not fully understood. Researchers and experts advise caution when applying these products as frequent applications are the norm among regular users of sunless tanners.
References
In Vivo Formation of Maillard Reaction Free Radicals in Mouse Skin
Cytotoxic, genotoxic, and toxicogenomic effects of dihydroxyacetone in human primary keratinocytes
