Seeds are used in cooking (poppy seeds) for cakes, bread, fruit salads etc. and are perfectly safe to eat, containing very little, if any, of the narcotic principles associated with the opium poppy.
Young leaves are apparently edible raw or cooked and must be used before the flower buds have formed, some caution is advised.
A wide range of alkaloids are extracted from the opium poppy for medicines, particularly for pain relief. These medicines should only ever be administered by a qualified medical practicioners as they are highly addictive.