This is probably one of the nastiest skin problems one has to encounter with. The red bump results from the infection of the hair follicle or gland and is filled with pus. They usually go away after the pus has drained.
11. Keratosis Pilaris.
Though harmless, it is kinda irritating to have your buttocks, thighs, and upper arms covered with small red colored spots. This is caused due the over production of the keratin pigment.
12. Allergic Reaction.
The most traditional reason of having red spots on your skin is a response due to an allergic reaction. This may be due to various kind of allergens, food, pollen, cosmetics. You just need to make sure that you avoid them.