Did you notice some painful, inflamed and red outgrowth on your skin? They are an ingrown hair. They are the result of frequent shaving, waxing and using various other methods to remove hair on the regular basis. They can even be an effect of dead skin that blocks hair follicles and forces the hair to grow inside. These are also known as razor bumps and are defined by raising curled hair and pimple-like red bump, which grows inwards in the skin instead of growing outside. It can cause pain, irritation and swelling on the skin. Usually, these are most common among people with curly hair.
source: How to Get Rid of Ingrown Hair ?