Bed stuffing: Certain bedding materials and fabrics like wool or feather-based materials may also cause allergic reactions in your pet. Hence, avoid them. Also, regularly clean the bedding. If nothing seems to work, talk to your vet.
Indoor plants: Your houseplants may also trigger airborne or contact allergic reactions in your pet. If you find it to be true, remove them soon.
To reduce allergens in your house (and thus your pet's chances of getting an allergic reaction), keep the surroundings clean. Also, make sure to remove all potential causes of allergy (try using hit-and-trial method). In the end, talk to your vet for treatment, if needed.