I was perfectly happy not knowing that this was possible. Or that someone would do that to themselves.
She eats her own hair, yet she has no idea why her stomach hurts. To quote Stanley Marsh; That's pretty f*cked up right there.
Cats do but tehy regurgitate it.
Only animal off hand I can think of that have stomach acid strong enough to dissolve hair and teeth is African Hyenas.
Hair isn't the only thing these folks ingest; it's a form of obsessive-compulsive behavior. In addition to hair, a variety of other undigestible items such as nuts and bolts, coins, nails, and so forth may be swallowed. I think the largest bezoar removed from a patient was over 100 pounds.
To me the dirt-eating, "geophagy", is just as bizarre. Arose in central Africa, still survives in the rural American South. Seems pregnant women did it more often, and perhaps it provided minerals to them.