Does ovex always work for threadworms ?

[Whatdoesitmatterif]

Sorry for the gross subject! I have ocd as it is and this worm situation is my actual living hell
5 year old has threadworms and we all took ovex a week ago, last night he woke up upset with an itchy bottom again but surely they should all be dead by now?
I know we need to re-dose after 2 weeks but any eggs that were left shouldn't have hatched and matured yet so it shouldn't be from re-infection yet, which is making me think is it possible the ovex didn't kill then in the first place?
I didn't see any worms this time tbf sk maybe it's itching from irritation after all the showering and washing and scratching etc?

I'd ask at the pharmacy or Dr's. Can't offer any advice but just a handhold as I'm going through this for the first time (literally trying to get her an app now)

The Ovex will only work if the hygiene stuff is done too to prevent ongoing re-infection because the medication kills the live worms not the eggs.

From the NHS site

Do

wash hands and scrub under fingernails – particularly before eating, after using the toilet or changing nappies

encourage children to wash hands regularly

bathe or shower every morning

rinse toothbrushes before using them

keep fingernails short

wash sleepwear, sheets, towels and soft toys (at a hot temperature)

disinfect kitchen and bathroom surfaces

vacuum and dust with a damp cloth

make sure children wear underwear at night – change it in the morning

Don’t

do not shake clothing or bedding, to prevent eggs landing on other surfaces

do not share towels or flannels

do not bite nails or suck thumbs and fingers

I've been doing all the hygiene stuff washing sheets, towels, pjs on a hot wash etc every day showering him every morning, he seemed ok after day 2 but now he's itching again, the first time around I saw them when I looked but this time can't see any sign of them.
there's a whole load of crazy people online who think threadworms are impossible to get rid of once you've had them and that they live in their nostrils and ears for years and things and i think that's really freaked me out!