all puppies need to be dewormed. once every 2 months until they are 6 months. then they will need to be dewormed every 6 months. only if you dog never leaves the house and your family doesnt either then you wont have to deworm your dog! but every body lesves the house so your pup can get worms. they can be in grass where otheranimals have been. the worm eggs lay dorment until some one comes along! it is possible that your pup has a worm infection. diarea and throwing up could be signs of worm infection. even if a dog is negitive when testing it needs not alot to get reinfected!