Is it normal to suck and eat hair

I'm doing this poll to prove to my nine year old brother that eating hair is seriously not good, and he should stop. Basically he is nine but he still sucks his thumb and finger a lot. If that's not bad enough, he wraps hair round his fingers and puts them in his mouth. It doesn't matter if it's his own hair (he used to have long hair but my mum had it cut short because he kept pulling it out and eating it), mine, someone else's or just one he finds on the floor. He has sucked ones from the showers at the swimming pool before. It is so gross. He has pulled my hair out before. Please help to show him that what he's doing is bad.