How to get rid of pinworms in a four year old. tried pinx and works for while but keep coming back.

Break the cycle: Though anti-parasitics work very well on pinworms, it isn't the drug that is the problem- you child is like reinfecting him/herself by fingers on the anus or placing them in an environment with pinworm eggs (i.e. Sandbox play) then placing the contaminated fingers into the mouth without washing them. Excellent hand hygiene and vigilant watching will hopefully prevent this cycle.