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Paracelsus' poison

Fake Tan but Real Damage?

It is a truth universally acknowledged that a person in want of coolness is in want of a tan. And increasingly, that tan is coming out of a bottle. To get the kind of deep-all over tan that Aussie legend is made of takes hours out in the sun that could be better spent playing the latest sporting game on your computer console du Jour. And let’s not forget Australia’s world record skin cancer rates, as the SunSmart message gets through our tans now follow the shape of the rashies we wear.

So, if we are off to a special event and don’t want to look like pallid addicts of daytime reality shows/computer games, more and more Australians put on a fake tan. A recent American expose may have people thinking twice or even thrice before slapping on that tan. As it turns out, there are some things to be concerned about, but they are not really what you might think.

dihydroxyacetone visualised with JMol. Ian Musgrave

At the heart of the worry is a chemical with the unprepossessing name of dihydroxyacetone (DHA, not to be confused with another DHA, Docosahexaenoic acid, which is used as a food supplement). This is the active ingredient of most fake sprayon tans. Sounds toxic doesn’t it? Well, it’s actually a simple sugar you body makes as part of normal metabolism. Your cells will happily slurp it up and burn it for fuel.

But your body makes formaldehyde too, and you wouldn’t want to slather that on your skin. What it comes down to is the dose, and, as readers of this column know by now (say it after me), it’s the dose that makes the poison.

The brown of crusty bread comes from the same reactions that allow DHA to turn skin brown. Ian Musgrave

You know the wonderful brown of a crusty loaf of bread? Well the same chemical reaction between sugars and proteins in the bread dough that makes the crust brown is how DHA makes your skin brown. Because DHA is more reactive than sugars like glucose though, you don’t have to sit in an oven for half an hour or so.

Glucose, although much slower at reacting than DHA, can also do these reactions at body temperature. One of the problems that diabetics can have is that after many years of high blood glucose levels, the slow reaction of glucose with the proteins in their blood vessels damages them and leads to circulation problems, kidney problems and eye problems.

So, even though DHA is an important metabolic fuel, you might suspect that high levels would cause problems. And if we incubate bacteria or mammalian cells with high concentrations of DHA, we find that the cause the sorts of damage that we suspect will lead to cancer and other problems. Of course, marinating a thin layer of cells in a petri dish with high concentrations of DHA doesn’t exactly mimic what happens when you slather it on your skin.

After all, the brown colouring you crave is due to the DHA reacting with the outer layers of keratin in your skin. Only a minute fraction of what you apply to your skin gets anywhere near living cells, which will promptly slurp it up to use as fuel. When we give very large doses of DHA to animals, for a very long time, very little happens to them.

In toxicological terms, the difference between what you get exposed to through your skin, and the lowest levels that are seen to cause effects in animals, is the Margin of Safety. The Margin of Safety for DHA applied to the skin is around a thousand fold for the worst case exposures we can think of.

But, and you knew there would be a but didn’t you, this is for DHA applied to skin, which is okay if you are rubbing on a lotion or cream. But what has happened in the last few years, and the focus of the American ABC report, is the rise of the spray tan.

While DHA wending it’s way through layers of keratin is vastly reduced in concentration before it reaches any living cells, what happens if we breath in droplets of spray?

Droplets of spray with relatively high concentrations could come in direct contact with the living cells lining the nose and lungs. This will be still be a relatively small dose, as only a fraction of the fine spray will get in, but still the effects of low, persistent exposure of these tissues to DHA is unclear.

In theory, people getting spray tans (at least in the US and Denmark), should be instructed to keep their mouths closed and be wearing nose filters (there are a number of different spray methods, and the exact details of the filter systems will be different for each method). But the issue found by the American ABC was that these instructions were not being followed. In Australia, my very, very small informal survey suggests that nose filers are not used here either.

Even then, the customers are at relatively low risk, even if they come back once a week, every week of the year. The ones at higher risk are the attendants running the booths. They are further away from the mists produced, but they are there every day of the week. Unless the salon has adequate air flow and exhaust fans, the possibility of chronic exposure the DHA is quite real, and we have no idea what the consequences of this exposure is.

There is no need to panic, but if you do indulge in spray on tans, it would be a good idea to be moderate in your use, and go to salons that use best practise safety. If you run one of these salons, please check the is adequate ventilation and air exhaust to lower your exposure.

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