According to HowStuffWorks, laser hair removal is safe to use on underarms. The procedure, which is not harsh to the skin, causes little pain and is completed in about 10 minutes.
WebMD points out that laser hair removal targets coarse, dark hair in particular but doesn't damage surrounding skin. After three to five laser hair removal sessions, hair is typically removed permanently.
As HowStuffWorks explains, laser hair removal works best on dark hair due to the laser's attraction to melanin. It is less effective on blond, gray or red hair. It works by affecting a hair follicle so that it no longer grows hair.