Pets are common causes of nasal allergies. This includes cats, dogs, birds, horses, and rabbits. Flakes of skin (dander), saliva left on fur when an animal cleans itself, urine in litter boxes and cages, and feathers can all cause nasal allergies. Pests, such as rodents, can also be a major cause of allergies. This is especially the case in urban settings. They may not even be in your own apartment.