Photo of girl holding a kitten (PantherMedia / ProfStocker)

Some people start sneezing or get a runny nose when they’re around certain animals, like cats or dogs. Many then say that they’re allergic to the animal’s fur. But it isn’t the fur that triggers an allergic reaction. Instead, it’s proteins that are found in the animal’s dander (flakes of skin), sweat, skin oil, saliva (spit), urine and feces ("poop").

These allergy triggers (allergens) stick to the animal’s fur and end up on objects like carpets or upholstered furniture. But particles with the protein on them also float through the air and spread in that way. The allergens enter the body through the airways or through direct physical contact.


The typical allergy symptoms usually start immediately after coming into contact with the allergen. Respiratory symptoms (affecting the airways) are the most common. They occur when people breathe in small particles with the protein on them. This usually causes a runny or stuffy nose and sneezing. Allergic rhinitis might develop into asthma after several years.

Animal allergens can also make your eyes water and itch. Hives (nettle rash) and skin rashes may occur too, but they’re less common.

Causes and risk factors

The following table lists the animals that are most likely to cause allergies, and how the allergens are usually spread:

Animals Allergens mainly spread through:
Cats Fur, saliva
Dogs Fur, saliva
Guinea pigs Urine
Horses Hair
Birds Feathers, excretions

The allergens can also be spread through animal fur on objects like mattresses, upholstered furniture, carpets, rugs and clothes. Farm animals such as cattle, sheep and chickens can cause allergies too.

Sometimes the allergens are found in places where there aren’t any animals. This is particularly true for cat allergens, which can easily be spread through tiny particles that float through the air. They may first settle on clothes, for instance, and then be spread to furniture from there. The allergens remain intact for a very long time, and can still trigger allergies months or years after leaving the animal. So, before moving into a new home, it’s a good idea to find out whether the people who lived there before you had cats.


Allergy symptoms can have a range of causes. It’s often hard to be sure whether they’re being caused by allergens on a pet or, for instance, dust mites. So it’s important to get things checked out by a doctor. Skin tests and blood tests can be done to see whether various allergens trigger an allergic reaction. In skin allergy tests, solutions containing potential allergens are placed on gently scraped skin, and the skin is observed to see whether it turns red or itchy. In blood tests, the doctor checks whether there are antibodies to animal allergens in the blood.

Sometimes people need to have a provocation test too. This has to be done under medical supervision. Provocation tests usually involve repeatedly exposing membranes lining the nose or eyes (conjunctiva) to increasing doses of potential allergens, and observing how the immune system reacts.


Not having any pets yourself usually doesn’t prevent you from developing a pet allergy. Some people have a cat allergy, for instance, even though they have never had any cats as pets. But if someone is at higher risk of developing allergies to animals, getting a pet could make them have pet allergy symptoms for the first time. On the other hand, though, it is believed that living with animals may actually prevent allergies. This could have something to do with the fact that regular close contact with allergens and microbes helps the immune system to learn how to tell the difference between harmless substances and harmful substances.

But it isn’t yet clear how living with animals affects the risk of developing allergies in the long term. It may not even have any influence at all, depending on things like what kind of animal it is and how much contact you have with it.


If you know what animal you are allergic to, it can help to avoid contact with that animal. It can also make sense to thoroughly wash your clothes, and clean or remove furniture. You may have to find a new home for your pet, depending on how severe your symptoms are, the treatment options and – last but not least – how close you are to each other.

Allergy symptoms can be relieved with medication. Nasal sprays and tablets for allergies can be used to treat the symptoms of allergic rhinitis (e.g. sneezing, a runny or stuffy nose, and itchy eyes, ears nose and throat). Rashes can be treated with steroid medications such as steroid creams.

Allergen-specific immunotherapy (desensitization) is a treatment option for cat allergies, among others. It may be considered if the symptoms are particularly severe and if contact with the animal can’t be avoided. Allergen-specific immunotherapy involves regularly exposing the body to small doses of the allergen over a time period of three to five years. This is meant to make the immune system react less sensitively to the allergen.

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