What sort of Allergies can Parakeets (budgies) have?

One bird allergy that I know of is Allergic Alvolitis. This is a respiratory hypersensitivity reaction (allergic reaction) to repeated inhalation of organic particles. Synonyms include extrinsic allergic alveolitis, budgerigar dander pneumonicosis, bird breeder's disease, allergic interstitial pneumonitis and pigeon breeder's lung.