There may be an hereditary element to it, as with most things, that could predispose any dog to being affected with an allergy but it could be multifactoral as well. As an example, the predisposition to allergies may well be inherited but that may not necessarily mean the allergy will manifest itself unless there is another factor involved, such as stress at any given time, or reaction to a medicine, trauma etc etc.
If Amy is the only one out of her litter at the moment then that to me, as a breeder, wouldn't give me enough reason not to breed again but I would look more closely at the stud dog lines and ascertain whether any of his relatives had similiar issues.
Hope that makes sense!
Becky