The product in question is He Shi's Gradual Self Tanner, which is from a brand that has been circulating the blogosphere for some time now. I was rather intrigued about this brand and was happy to try out the self-tanner. Ordinarily, I am not one for tanning, naturally or otherwise. I can't spend hours basking in the sun without thinking of those staying safe in the sun adverts and honestly do not want to damage my skin for the sake of a bit of colour. Don't get me wrong, I love laying on a beach as much as the next person, but believe in doing it safely. That's why I'm not opposed to fake tanners, if it's done tastefully, in other words you haven't made yourself orange. Personally I don't have the time or patience for fake tan, but I was curious to try a gradual tanner as they work slightly differently to your standard fake tan.
The sciencey bit: basically, the active ingredient that makes any self tanner work is dihydroxyacetone or DHA for short. It's essentially a type of sugar and when applied to your skin, reacts with the top layer to brown it in a similar way that food browns when it's left exposed to air. Since it is just the top layer of skin that the DHA reacts with, it lasts for just a couple of days until that layer of skin has been washed away. Gradual tanners have a much lower concentration of this ingredient than regular fake-tan which makes the effect more subtle and allows you to build up the tan gradually.