It's finally summer! But after having spent so many months indoors, you might look a little pale. Getting a tan takes a while, especially when you're protecting yourself with sunscreen! If you're really in a hurry to turn a few shades darker (and pretend you've spent your time at the beach instead of in a stuffy classroom), you can always try fake tanners. So how can you get a tan from a bottle?

Let's start with how you can get a tan the regular way — from the sun. Your skin is made up of several layers. The outer part is called the epidermis, and even that is divided into multiple layers! The part of the skin you can see is just the outer layer of dead cells, but further down, other cells of the epidermis are alive and working hard at producing the skin pigment melanin.

Did you know? Melanin production is regulated by more than a hundred different genes. The amount of melanin that they produce is different for everyone, which is why we don't all have the same skin colour.

Cells that produce melanin are called melanocytes. Once made, the melanin that is transferred to other cells in the epidermis, so they get pigment too, (even if they don't make it themselves). Melanin protects the nucleus of skin cells from UV radiation. The nucleus contains DNA, and UV radiation from the sun can damage the DNA and cause skin cancer. Melanin forms a shield inside the cell to block the UV radiation. Like sunglasses for your DNA! When you're out in the sun, the UV radiation gets stronger, so the melanocytes will make more melanin to try to protect the DNA as much as possible. This is what tanning is: it's your body's defense against harmful radiation.

Did you know? Melanin can't completely block the nucleus from UV radiation, so you're not safe from DNA damage, even with a tan. Always wear sunscreen to protect yourself!

Now you know how regular tanning works, but what about fake tanning? That's a different story. There are a few different types of fake tanning products. The most popular ones are products like Fake Bake and the type used in tanning booths, so let's start with those. These products all contain a chemical called dihydroxyacetone (DHA). DHA is produced from sugar beets or sugar cane. It's colourless, but when it comes in contact with amino acids in the dead cells of the outer layer of your skin it will turn brown. This is called a maillard reaction and is the same type of chemical reaction that gives coffee and bread crusts their brown colour!

Did you know? Even though DHA is colourless, fake tanners are often coloured. That's just an added colour so you can see it better when you apply it.

DHA only colours the outside dead layer of the skin and only lasts as long as the dead cells stay on your skin. These cells regularly come off, and get replaced by dying cells from lower skin layers. When the cells are gone, so is your tan!

Did you know? In about a month, all your dead skin cells will have sloughed off and been replaced by new ones.

The pigment produced by DHA offers only a bit of protection against UV radiation, so remember - you should still use a good sunscreen!

About self-tanners:

http://www.medicinenet.com/script/main/art.asp?articlekey=23898

History and chemistry of DHA in self-tanning products:

http://dihydroxyacetone.com/dhainfo

Layers of the skin:

http://training.seer.cancer.gov/ss_module14_melanoma/unit02_sec02_anatomy.html

Eva Amsen is finishing a PhD in Biochemistry at the University of Toronto. This summer, instead of enjoying the sun and actively producing melanin, she is writing her thesis about melanin and melanocytes.

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