“Sun-kissed skin”, “radiant”, “bronze”, and a “healthy glow” – these are just a few of the many descriptors trending on social media and in the beauty industry worldwide, especially in Western countries. While this look could possibly be achieved by a few sun-drenched days at the beach, many people are now opting for sunless alternatives to tanning. Q: That seems recent – so what’s up with the title? While it is true that the original Bronze Age lasted for many centuries and fake tanning is a relatively recent phenomenon, the “Modern Bronze Age” is just a term used by popular media to describe the era of the fake-tan – playing on the word “bronze” to describe the generally desired outcome of a fake tan. From celebrities to the former US president Donald Trump (footnote 1) [1], it seems that sunless tanning products, such as tanning beds, lotions, and sprays, are in extensive use. Many people from countries where a sunny day is a rarity turn to fake tanning as a solution, and they have the scientist Eva Wittgenstein to thank for her discovery. Q: How did one stumble upon a fake tan? As with many scientific discoveries, one did not set out to find or develop a fake tan. While investigating the oral application of a chemical compound known as DHA (dihydroxyacetone; not to confuse with the omega-3 fatty acid (docosahexaenoic acid) in fish oil) for children with glycogen defects, she observed the noticeable coloration of skin where the DHA spilled. This was not the first time this skin-browning effect was noticed by scientists – German scientists in the 1920s had already done so – but it was the first time for DHA to be considered for cosmetic purposes [2]. Wittgenstein researched this further and published a paper in 1960 to explain how DHA produced an “artificial tan” [3]. Q: Wow! So, you’re telling me, I can just use a lotion at home and get a tan without having to suffer outside during the summer. How does that work? Could it also offer me sun protection? This may come as a surprise, but this process of skinbrowning follows the same reaction responsible for the browning of bread and roast meat, known as the Maillard reaction. Our skin is composed of a few layers, and the outer surface comprises a layer of dead skin cells. The Maillard reaction between the amino acids in this outer layer and the colorless DHA produces the brown pigment melanoidins [2]. Nevertheless, the process is not instantaneous. After two to three hours, the skin begins to acquire a tan and the reaction carries on for another one to three days [2, 4]. Once formed, melanoidins can't be washed off by water, soap, or moisturizer until the skin cells are shed. [2, 4]. The browning effect can last for one week [2, 4]. However, unlike the pigment melanin in natural tanning, melanoidins don’t offer much ultraviolet (UV) protection on their own (Figure 1). It’s estimated that most of these sunless tanners can offer only a meager SPF of 3, which is not nearly enough sun protection [2]. Therefore, it’s extremely important to wear sunscreen with adequate SPF when going outdoors, with or without a sunless tan. Q: That story does not fill me with a whole lot of confidence about fake tanning, and the cosmetic industry has a history of being misleading to sell us products. What do scientists have to say about its safety? By Aastha Shreeharsh Fake Tan 摩登青銅時代 美黑霜 The Modern Bronze Age:
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