You can spot worms in your baby's poop, and you might also see them in your baby's bottom. They look like pieces of white thread, and they usually come out at night while your child is sleeping. The symptoms can be extreme itching and irritability around the anus, particularly at night, wetting the bed, and waking up frequently. You can buy mebendazole from the pharmacy in tablets or liquid form and treat everyone in your household even if they don't have symptoms.