what causes razor bumps after shaving?

It's called 'Pseudofolliculitis barbae'. I got what follows from http://en.wikipedia.org/wiki/Pseudofolliculitis_barbae [i]PFB is most common on the male face, but it can also happen on other parts of the body where hair is shaved or plucked, especially areas where hair is curly and the skin is sensitive, such as genital shaving (more properly termed pseudofolliculitis pubis or PFP). After a hair has been shaved, it begins to grow back. Curly hair tends to curl into the skin instead of straight out the follicle, leading to an inflammation reaction. PFB can make the skin look itchy and red, and in some cases, it can even look like pimples. These inflamed papules or pustules can form especially if the area becomes infected. This is especially problematic for men of African descent and other people with curly hair. If left untreated over time, this can cause keloid scarring in the beard area. Pseudofolliculitis Barbae can further be divided into two types of ingrown hairs: transfollicular and extrafollicular. The extrafollicular hair is a hair that has exited the follicle and reentered the skin. The transfollicular hair never exits the follicle, but because of its naturally curly nature curls back into the follicle causing fluid build-up and irritation. Men of African, Mediterranean, Jewish descent, and other peoples who have naturally coarse or tightly curling hair will often get 'razor bumps' in their beards.[/i] Apparently, it is worse for people with curly hair. I don't think there is anything that can be done to prevent it besides not shaving. Maybe laser hair removal or electrolysis can be used to permanantly stop the hair from growing, thus preventing the bumps and scarring to build up.