This is the 3rd time i have had pinworms in a year. this time they are back, mebendazole seems to be inneffective. i also have stomach pain and nausea?

Work with doctor: In the US, pin worms are more common in children, but there may be a different pattern of infection in Catalonia. Pin worms are a parasite; typically Mebendazole or Albendazole is used for treatment. The pin worm does infect the digestive tract; this or the Mebendazole could be causing stomach symptoms. Hygiene is key: morning shower, changing underwear & bed linen, wash in hot water, clean toilet

Is it really: The only way you would get it repeatedly is to be exposed to and consume the eggs.If you don't have a bunch of toddlers running around re-infecting you a new approach may be needed.Not all itchy bottoms are due to pinworms. A variety of food allergies, bacterial and yeast infections can cause the same symptom. Unless you/doc are verifying the infection by testing it may not be.