Will worm medicane damage him if he doesnt have them

My cousin has had a rather itchy bum lately, and so his mother wants to buy worm tablets for those 'string woms' or something... but what if he says he cant see any? Will taking this medicane to him any harm? And can you get it over the counter at a chemists, or does he need a perscription?
Thankyou a bunch!
Love Charly <3

He needs to go to the doctor and get a stool test to see what's there. That way the doctor can prescribe the right thing. And, none of the worm medicine is too pleasant. I sure wouldn't just grab some random OTC thing at the drug store and take it.

No, they won't do any harm as long as he doesn't over dose , plus if he really had them it would actually help!
and no,you don't need a prescription for that.