The bane of barbers everywhere.
Hair is actually extremely sharp, but most people don't realize this because they're usually dealing with fallen hair of a sufficient length and flex that it won't do what it does when it gets trimmed to 1/8" or less.
When it does get to that length, either by being clipped off in a buzz cut or by being trimmed off the ends - it can and does bury itself into the skin occasionally, hurting just as much as any metal or wood sliver that gets forced under the skin. It has a tendency to find its way into natural creases in hands, fingers and so forth and when you grab something with it poking into the skin, it gets driven into the skin painfully. And it's just as painful for the free end to be flexed backwards.
It can also get into your shoes and bury itself in your feet, get into your clothing and bury itself into body skin, and so forth. But it's usually in the hands where it causes problems, and God forbid you deal with an ash blonde, because finding it against skin tones is nigh on impossible.