Most allergies are inherited, which means they are passed on to children by their parents. Although people inherit a tendency to be allergic, they may not inherit an allergy to the same allergen. When one parent is allergic, their child has a 50% chance of having allergies. That risk jumps to 75% if both parents have allergies.
Typically, an allergic response is not triggered the first time the body encounters the allergen. The first or several times after the body is exposed to an allergen, the immune system becomes sensitized. During this process, the body's white blood cells develop immunoglobulin E (IgE) antibodies to the allergens in the pet dander. Once sensitized, the antibodies quickly detect and bind to the pet dander allergens in the body. These antibodies also trigger the release of chemicals (like histamine) that cause allergic symptoms, such as runny nose, watery eyes and sneezing.
Allergies to animals can take two or more years to develop, and allergy symptoms may not subside until months after discontinuing contact with the animal. Individuals who want to keep their animal can make lifestyle changes or take allergy medications like antihistamines to control their symptoms.
The actual fur and hair of the animal does not trigger allergic reactions. Animals secrete oily fluids, which contain the allergens. These fluids collect on the fur, feathers and other surfaces inside the home. These allergens are so small that they can become airborne for extended periods of time. Inhaling the airborne allergens can also trigger an allergic reaction. The more the pet sheds or molts, the more pet dander is present. Proteins in the animal's saliva may also be responsible for allergic reactions. These allergens are capable of triggering reactions for several months.
Pet dander is often found in homes without animals because the dander can be carried on people's clothing. The allergens become airborne when the animal is petted or groomed, when the animal sheds, molts, or grooms itself or when the air is stirred where the allergens have settled.
The severity of allergy symptoms varies among individuals, and does not necessarily correlate with the length of time exposed to the allergen. Individuals who have minor allergies may not experience symptoms until several days after contact with the pet. Highly sensitive individuals may experience symptoms within 15 to 30 minutes of exposure.
Common symptoms include stuffy nose, coughing, wheezing, shortness of breath, sinusitis (allergic inflammation of the sinuses), allergic rhinitis (inflammation of the nose), as well as swollen, red and itchy eyes. Rhinoconjunctivitis (inflammation of the nose and eyes in response to an allergen) may also occur. Highly sensitive individuals may experience an intense rash on the face, neck and upper chest. If the animal licks an allergic individual, the skin may become red.
Allergies are commonly associated with asthma. It is estimated that about 20-30% of people who have asthma may experience a severe asthma attack after contact with a cat. Asthma symptoms may include bronchospasms (abnormal contraction of the bronchi, resulting in airway obstruction), coughing (constantly or intermittently), wheezing or whistling sounds when exhaling, shortness of breath or rapid breathing, chest tightness or chest pain and fatigue.
Skin test: The standard diagnostic test for pet allergies is a skin test. During the test, the skin is exposed to different allergy-causing substances, including pet dander. The skin is then observed for any signs of an allergic reaction. If an allergen triggers an allergic reaction to a test, the patient will develop reddening, swelling or a raised, itchy red wheal (bump) that looks similar to a mosquito bite. The healthcare provider will measure the size of the wheal and record the results. The larger the wheal, the more severe the allergy is. A skin test is typically conducted in a healthcare provider's office, and causes minimal, if any discomfort. The needles used barely penetrate the skin's surface and will not cause bleeding.
Allergen-specific immunoglobulin (IgE) test: An allergen-specific immunoglobulin E (IgE) test, commonly referred to as a radioallergosorbent test (RAST®), may also be used to determine whether the patient is allergic to animal dander. However, this test is less accurate than a skin test. The allergen-specific IgE test is usually performed in patients who have severe, coexisting skin diseases (like eczema or psoriasis) that make it difficult to interpret a skin test.
The in vitro test is conducted outside of the body in a laboratory setting. During the procedure a sample of blood is taken from the patient. The blood is then sent to a laboratory that performs specific IgE blood tests. The pet dander allergen is bound to an allergosorbent (paper disk). Then the patient's blood is added. If the blood contains antibodies (immunoglobulins that detect and bind to antigens) to the pet dander, the blood will bind to the allergen on the disc. A radiolabelled ANTI-IgE antibody is then added to the disc to measure the level of IgE present in the blood. The higher the radioactivity, the higher the level of IgE in the blood and the more severe the allergy.
A qualified healthcare provider will interpret the results of the test. In general, the sensitivity of these tests range from 50-90%, with the average being about 70-75%. Patients receive test results in about 7-14 days.