Pet allergy

For some people, pet allergy may be the primary cause of inflammation and contraction of airways of the lungs (asthma), resulting in wheezing, shortness of breath and other breathing difficulties.

Any animal with fur can be a source of pet allergy, but pet allergies are most commonly associated with cats, dogs, rodents and horses. Although pet allergy, or animal allergy, is most often a "household problem," it can also affect people who work with animals on farms, in laboratories and in zoos.

If you have a pet allergy, the best strategy is to avoid or reduce exposure to the animal as much as possible. Medications or other treatments may be necessary to relieve symptoms and manage asthma.

Symptoms

Pet allergy symptoms caused by inflammation of nasal passages include:

• Sneezing
• Runny nose
• Itchy, red or watery eyes
• Nasal congestion
• Itchy nose, roof of mouth or throat
• Postnasal drip
• Cough
• Facial pressure and pain
• Frequent awakening
• Swollen, blue-colored skin under your eyes
• In a child, frequent upward rubbing of the nose

If your pet allergy contributes to asthma, you may also experience:

• Difficulty breathing
• Chest tightness or pain
• Audible whistling or wheezing sound when exhaling
• Trouble sleeping caused by shortness of breath, coughing or wheezing
• Bouts of coughing or wheezing that are worsened by a respiratory virus such as a cold or the flu

Skin symptoms

Some people with pet allergy may also experience skin symptoms. Allergic dermatitis is an immune system reaction that causes skin inflammation. Direct contact with an allergy-causing pet may trigger allergic dermatitis symptoms, which may include:

• Raised, red patches of skin (hives)
• Itchy skin

Causes

An allergic reaction is somewhat like a case of mistaken identity within your body's immune system. Normally, your immune system generates antibodies to protect your body against bacteria, viruses or toxic substances.

If you have a pet allergy, your body generates an allergy-causing antibody to a protein found either in an animal's skin cells, saliva or urine. In other words, your immune system mistakenly identified this protein as something that could harm you. Once your body has developed an allergy-causing antibody to a particular agent (allergen) — in this case, an animal protein — your immune system will be sensitive to it. When you inhale the allergen or come into contact with it, your immune system responds and produces an inflammatory response in your nasal passages or lungs.

A pet allergen can cause two kinds of immune system responses in the airways of your lungs. An allergen can prompt inflammation in air passages. Therefore, prolonged or regular exposure to the allergen can cause the ongoing (chronic) inflammation associated with asthma. Exposure to an allergen also may cause sudden, severe constriction of air passages (bronchospasms).

Cats and dogs

Allergens from cats and dogs are found in skin cells the animals shed (dander), in saliva and on hairs. 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. Dried saliva can become airborne.

Some breeds of dogs are considered "hypoallergenic," or less likely to trigger allergies, because they don't shed fur. While the absence of shed fur may reduce exposure to dog allergens, a person allergic to dogs would still be allergic to nonshedding breeds.

Rodents and rabbits

Rodent pets include mice, gerbils, hamsters and guinea pigs. Allergens from rodents are usually present in hair, dander, saliva and urine. Dust from litter or sawdust in the bottom of cages may contribute to airborne allergens from rodents.

Rabbit allergens are present in dander, hair and saliva.

Other pets

Pet allergy is rarely caused by animals that don't have fur, such as birds, fish and reptiles. 

Risk factors

Pet allergies are common. However, you're more likely to develop sensitivity to pet allergens if allergies or asthma runs in your family.

Research about the effect of early exposure to pets and the risk of allergy and asthma is inconsistent. However, a number of studies suggest that exposure to cats in early childhood may slightly decrease the risk of cat allergy. Other studies suggest that early exposure to dogs has no effect on risk or only slightly increases the risk.

Complications

Sinus infections

Ongoing (chronic) inflammation of tissues in the nasal passages caused by pet allergy can obstruct your sinuses, the hollow cavities connected to your nasal passages. These obstructions may make you more likely to develop bacterial infections of the sinuses, such as sinusitis.

Asthma

People with asthma and pet allergy often have difficulty managing asthma symptoms. They may be at risk of asthma attacks that require immediate medical treatment or emergency care. 

Diagnosis

Your doctor may suspect pet allergy based on symptoms, an examination of your nose and your answers to his or her questions. He or she may use a lighted instrument to look at the condition of the lining of your nose. If you have a pet allergy, the lining of the nasal passage may be swollen or appear pale or bluish.

Your doctor may suspect a pet allergy, based on your comments. For example, you may have a pet allergy if your symptoms are worse when you have direct contact with your pet or when your pet sleeps in your bedroom or on the bed.

Allergy skin test

Your doctor may suggest an allergy skin test to determine exactly what you're allergic to. You may be referred to an allergy specialist (allergist) for this test.

In this test, tiny drops of purified allergen extracts — including extracts with animal proteins — are pricked into your skin's surface. This is usually carried out on the forearm, but it may be done on the upper back.

The drops are left on your skin for 15 minutes before your doctor or nurse observes your skin for signs of allergic reactions. If you're allergic to cats, for example, you'll develop a red, itchy bump where the cat extract was pricked into your skin. The most common side effects of these skin tests are itching and redness. These side effects usually go away within 30 minutes.

Blood test

In some cases a skin test can't be performed because of the presence of a skin condition or because of interactions with certain medications. As an alternative, your doctor may order a blood test that screens your blood for specific allergy-causing antibodies to various common allergens, including various animals. This test may also indicate how sensitive you are to an allergen. 

References

http://www.webmd.com/allergies/guide/dog-allergies

http://www.healthline.com/health/allergies/dog#Treatment4

https://www.hse.ie/eng/health/az/A/Allergies/Diagnosing-an-allergy.html

http://www.thelancet.com/pdfs/journals/lancet/PIIS0140673602099063.pdf