Pet allergy is an allergic reaction to proteins found in an animal's skin cells or flakes, saliva or urine. Most often the allergy is to cats or dogs, but rats, mice, guinea pigs, hamsters, pet birds, horses, cows or poultry can also be involved. Allergens from cats and dogs are found in skin cells the animals shed (dander), on hairs and in saliva. Dander is a particular problem because it is very small and can remain airborne for long periods of time with the slightest bit of air circulation. It also collects easily in upholstered furniture and sticks to your clothes. Pet saliva can stick to carpets, bedding, furniture and clothing.

Rabbit allergens are also present in dander, hair and saliva. Allergens from rodents are usually present in hair, dander, and saliva but also in urine. Thereafter, dust from litter or sawdust in the bottom of cages may contribute to airborne allergens from rodents. Both saliva and urine can dry and small particles become airborne and thus penetrate in the human organism. People also develop allergies to animal droppings, especially bird droppings. Pet allergens can come from other people's pets or be transported by people who have been in contact with animals. This is why pet allergens have been found in school classrooms. mouldSigns of pet allergy include those common to hay fever, such as conjunctivitis, sneezing and runny nose. Some people may also experience signs of asthma, such as wheezing and difficulty breathing. Pet allergy may also be involved in inducing atopic dermatitis. If you have pet allergy, you should avoid having contact with them.

Although cat and dog are known sources of allergens, their role in the development of allergic sensitization and allergic disease is less clear and remains a subject of debate. Indeed recent studies suggest that pet exposure, particularly in the first months of childhood and to high doses, may prevent the development of atopic disorders.