Many people are allergic to the proteins in the skin cells or saliva of dogs. If a dog sheds, it is more likely to spread more dead skin cells (dander) along with its hair. However, many allergen researchers are skeptical that the term hypoallergenic should be used for any dog breed whether it sheds or not.
While no dog is safe for allergy suffers to be around, some breeds shed very little or not at all. The Poodle is hypoallergenic which, along with its intelligence, may a reason it is often used for designer dogs.