2 Year Old Child, Itching In Rectum, Vomiting. Thread Worm Infection?

hi, last night my 2+ yr old son was having itching around Poo are.....it occurs suddenly at 9 O clock and disturbed him until he had one throw throw up. after wards he slept properly and even since morning i am asking if he still have any itching and all the time he says No. Is he having any thread worm ..though i haven t seen any( as i read itching is symptoms of thread worm) ....and if it is not so what was that..what should i do at home when it happens again??