Introduction

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.

Symptoms

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:

The allergens can also be spread through animal fur on objects like mattresses, upholstered furniture (e.g. sofas, armchairs), 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.

Diagnosis

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. The skin prick test involves putting potential allergens on the forearm with enough space between them. The skin is gently pricked where the allergen solutions are, so the substances can get into the skin. Then 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.

You might also need a blood test or something known as a provocation test. This is where the membranes lining the nose or eyes (conjunctiva) are exposed to extracts of the potential allergen using a nasal spray or drops. If the lining of your nose becomes swollen, you sneeze and your nose starts running, you are likely to have allergic rhinitis.

Prevention

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 there's currently no scientific proof that this theory is true. The risk of becoming allergic to an animal you live with will depend on things like what kind of animal it is and how much contact you have with it.

Treatment

If you know what animal is causing your allergy, 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 don't always have to part with the pet. This will depend on severity of your symptoms and the treatment options, though.

The allergy symptoms can be relieved with medication. Nasal sprays and tablets for allergies can be used to treat the symptoms of allergic rhinitis. Rashes can be treated with steroid medications such as steroid creams.

Allergen-specific immunotherapy (desensitization) is a treatment option for cat allergies, among others. There's a lack of good research on whether it works well in the treatment of dog allergies. Immunotherapy may be considered if the symptoms are particularly severe and if contact with the animal can’t be avoided. The treatment involves regularly exposing the body to small doses of the allergen over a time period of at least three years. The aim is to train the body's immune system to become less sensitive (desensitize it) to the allergen.

Further information

When people are ill or need medical advice, they usually go to see their family doctor first. Read about how to find the right doctor, how to prepare for the appointment and what to remember.

Sources

• Biedermann T, Heppt W, Renz H, Röcken M (Ed). Allergologie. Berlin: Springer; 2016.
• Brozek JL, Bousquet J, Agache I, Agarwal A, Bachert C, Bosnic-Anticevich S et al. Allergic Rhinitis and its Impact on Asthma (ARIA) guidelines - 2016 revision. J Allergy Clin Immunol 2017; 140(4): 950-958. [PubMed: 28602936]
• Deutsche Gesellschaft für Allergologie und klinische Immunologie (DGAKI), Deutsche Gesellschaft für Kinder- und Jugendmedizin (DGKJ). Allergieprävention (S3-Leitlinie). AWMF-Registernr.: 061-016. 07.2014.
• Trautmann A, Kleine-Tebbe J. Allergologie in Klinik und Praxis. Stuttgart: Thieme; 2013.

• IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

  Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. We do not offer individual consultations.

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