Michifus - Quite a number of people can experience a darkening of the skin around the armpit region due to a number of different reasons such as obesity, diet, skin conditions, the use of chemical based deodorants and even wearing tight clothing! As you can imagine, having underarm skin which is darker than the rest of your body can affect your self confidence and many people will try to remedy this issue.
Sdbayquen - The DERMA kit works by peeling the top layer of the skin, which can have some visual effects but will not correct a melanin imbalance or a hyper pigmentation condition. It may also irritate the skin due to the sensitivity in this region. You can get more information on the mechanics of these kinds of products by reading https://hubpages.com/style/Underarm-Whitening