Skin and Cosmetics

Tanning: colour is not dose

Self-tanner colours only the dead outer layer of the skin: dihydroxyacetone (DHA), used at 4 to 8 per cent in most products, reacts with amino acids in the horny layer, shows within 1 to 8 hours and wears off with normal shedding in 3 to 10 days, with a UV dose of zero. A tan from the sun or a sunbed is the opposite, a defence reaction of living cells to UV damage: across 27 studies, ever using a sunbed raised melanoma risk by 20 per cent and first use before the age of 35 by 87 per cent. That is why more than 40 national or provincial authorities restrict sunbeds and why the UK, France, Germany and 22 US states, among others, keep anyone under 18 off them.

How self-tanner colours the skin

Self-tanner works on cells that are already dead. Its active ingredient, dihydroxyacetone (DHA), is a simple sugar that reacts with free amino acids in the stratum corneum, the outermost layer of the skin, in a Maillard reaction, the same type of browning that turns a bread crust golden. The products of that reaction, melanoidins, are brown pigments that sit in the horny layer and nowhere deeper. Products contain 1 to 15 per cent DHA, most of them 4 to 8 per cent. The first shift in colour begins about 1 hour after application, the full tone shows after 8 to 24 hours, and the colour leaves as the horny layer sheds, normally within 3 to 10 days, in practice 5 to 7 days for most people.

That mechanism explains the 3 things people get wrong about a fake tan. First, it is not a sun tan: no melanin is made, no UV has reached the skin, and no living cell has been touched. Second, it does not protect. Brown pigment in dead cells has no meaningful sun protection factor, which is why dermatology bodies on both sides of the Atlantic say you need the same SPF 30 with broad-spectrum UVA cover as untanned skin. Third, the reaction is not entirely inert: it produces some reactive oxygen species in the horny layer, and inhaled or swallowed DHA has never been approved anywhere. The FDA restricts DHA to external application away from the eyes, lips and mucous membranes, so a spray booth calls for nose filters, eye protection and a lip balm every single time.

An even result in five steps

The patchy look that gives fake tan its bad name has one cause: the horny layer is thicker in some places and takes up more DHA. Exfoliate 12 to 24 hours before application, with extra attention to knees, elbows, ankles and the backs of the heels. Shave or wax at least 24 hours before, never on the day, because freshly opened follicles show up as dark dots. Apply to dry, clean skin without moisturiser, except on the joints, where a thin layer of lotion or a self-tanner diluted 1 to 1 keeps the colour down. Wash your palms straight away, or use a mitt from the start.

Then leave it alone. Wait at least 10 minutes before dressing, wear loose clothing for the next 3 hours and avoid sweating, water and tight straps in that window. Judge the result at 24 hours, not at bedtime, because the tone keeps developing overnight. A gradual product used every 2 to 3 days keeps a steadier colour with fewer edges than one strong application a week. If something goes wrong, a gentle exfoliation shortens the 5 to 7 days it would take to fade on its own; there is no way to pull the colour out of the cells that hold it. If you have melasma or pigment spots, be aware that DHA darkens patches and background skin by the same amount, so uneven pigment stays uneven, only darker.

What a sunbed does to living skin

A sunbed delivers a real ultraviolet dose to living cells, mostly UVA with a share of UVB. The tan that follows is melanin produced in response to DNA damage, the skin's attempt to shield itself against the next dose. The International Agency for Research on Cancer moved UV-emitting tanning devices into its highest category, carcinogenic to humans, in 2009, the same group as tobacco and asbestos. The European device standard, mandatory since 2007, limits a sunbed's effective irradiance to 0.3 watts per square metre, which already equals a UV index of about 12, the Mediterranean sun at noon in summer. Whether that limit is kept is another matter: when 402 sunbeds in England were measured between 2010 and 2011, 9 out of 10 exceeded it, some by a factor of 6 compared with that midday sun.

The cancer figures come from a 2012 meta-analysis of 27 studies published in the BMJ. Ever using a sunbed raised the risk of melanoma by 20 per cent; first use before the age of 35 raised it by 87 per cent; each additional session per year added about 1.8 per cent. The authors calculated that in 2008 sunbeds caused about 3,438 melanomas and 794 melanoma deaths a year across 18 Western European countries. Melanoma is the rare but deadly form; the more common basal and squamous cell carcinomas rise as well, by roughly 24 and 58 per cent with indoor tanning according to figures compiled by the American Academy of Dermatology. The WHO counted more than 1.5 million skin cancers and 120,000 skin cancer deaths worldwide in 2020, and its fact sheet says plainly that a sunbed should never be used as a way to reach a sufficient vitamin D level.

What the law says, from London to Sydney

Regulators do not treat sunbeds as wellness. A WHO report from 2017 counts more than 40 national or provincial authorities that have banned or restricted them, and the pattern is the same almost everywhere: no access for anyone under 18. In the UK, the Sunbeds (Regulation) Act 2010 has made it an offence since April 2011 for a business to let an under-18 use a sunbed, in tanning salons as well as gyms, hotels and leisure centres. France set an under-18 limit as early as 1997, Germany followed in 2009, and Brazil banned commercial sunbeds outright in the same year. Australia, with some of the highest skin cancer rates in the world, closed commercial tanning salons in most states from 2015. In the United States, 22 states prohibit indoor tanning under 18, and the FDA moved sunlamps into a higher risk class in 2014 with a warning that they should not be used by anyone under 18.

Self-tanner sits on the other side of the same rulebook. In the EU it is an ordinary cosmetic product under the Cosmetics Regulation of 2009; in the United States DHA has been listed as a colour additive for external use for decades. That contrast is the whole point: one product is regulated like a shampoo, the other like a source of radiation, and the difference between them is the dose.

Colour, vitamin D or sun, three questions with three answers

If you want colour, use self-tanner. It gives the same visible result in 8 to 24 hours with a UV dose of zero, and at 8 to 30 EUR a bottle or 25 to 60 EUR for a salon spray tan it costs about as much as 3 to 6 sunbed sessions at 5 to 15 EUR each. If vitamin D is your worry, the answer is a supplement, not a lamp: the NHS recommends 10 micrograms a day for everyone from October to March, and all year round for people who are rarely outdoors or have darker skin, with 100 micrograms as the daily ceiling. Food and a few minutes of ordinary daylight cover the rest; a sunbed adds cancer risk to a problem that costs cents a day to solve.

If you are going into the sun anyway, a base tan from a sunbed buys almost nothing: dermatologists put its protection at the equivalent of SPF 3 or less, while the UV that produced it counts in full. Shade between 11 in the morning and 3 in the afternoon from spring to autumn, clothing, and a sunscreen with SPF 30 and 4-star UVA protection, 6 to 8 teaspoons for the whole body and reapplied every 2 hours, do more than any pre-tan. Protection starts at a UV index of 3, which the Sun Exposure Timer translates into minutes for your skin type. The long-term reason is cosmetic as much as medical: about 80 per cent of the visible ageing of the face is down to UV, as the radiance guide sets out. The tan of this summer is the age spot of 2046.

Before a spray tan or self-tanner at home

Frequently asked

Does self-tanner protect against the sun?

No. The colour forms in the dead horny layer and gives no sun protection factor worth the name, so you need the same SPF 30 with broad-spectrum UVA protection as untanned skin, reapplied every 2 hours outdoors.

How long does self-tanner last?

Between 3 and 10 days, for most people 5 to 7, until the coloured horny layer has shed. Exfoliating 12 to 24 hours before application and a gradual product every 2 to 3 days keep the colour even.

Why do knees and elbows go darker?

Because the horny layer is thicker there and takes up more DHA. Exfoliate those areas first and apply the product thinly or diluted 1 to 1 with lotion on knees, elbows and ankles.

Can people under 18 use a sunbed?

In most regulated markets, no. The UK has banned it since 2011, France since 1997, Germany since 2009, and 22 US states have the same rule; a WHO report from 2017 counts more than 40 national or provincial authorities with bans or restrictions.

Is a sunbed tan safer than a tan from the sun?

No. Both are a defence reaction to UV damage, and a sunbed at the European limit of 0.3 W/m² already matches a UV index of 12. Sunbed use raises melanoma risk by 20 per cent overall and by 87 per cent when it starts before the age of 35.

Can I use a sunbed for vitamin D?

The WHO says artificial tanning should never be used to reach a sufficient vitamin D level. A supplement of 10 micrograms a day from October to March, as the NHS recommends, covers the gap without any UV dose.

Sources

• Boniol M et al., Cutaneous melanoma attributable to sunbed use: systematic review and meta-analysis, BMJ 2012 · 27 studies; relative risk 1.20 for ever use, 1.87 for first use before 35; 1.8 per cent per additional session a year; 3,438 melanomas and 794 deaths in 2008 across 18 Western European countries
• WHO fact sheet: Ultraviolet radiation · 1.5 million skin cancers and 120,000 deaths in 2020; protection from UV index 3; sunbed use raises skin cancer risk and is never an option for vitamin D
• NHS: Sunscreen and sun safety · SPF 30 and 4-star UVA, 11am to 3pm from March to October, 6 to 8 teaspoons, reapply every 2 hours; sunbeds illegal under 18
• DermNet: Dihydroxyacetone · Maillard reaction in the stratum corneum; 1 to 15 per cent DHA, mostly 4 to 8; colour from 1 hour, peak 8 to 24 hours, lasts 3 to 10 days; no replacement for sun protection

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This guide is for general information. It does not replace medical or professional cosmetic advice or an examination.