Normally, the human body defends itself against harmful substances such as viruses or bacteria, but, sometimes, the defenses aggressively attack usually innocuous substances such as animal proteins, dust, mold or pollen.

The immune system generates large amounts of the antibodies called immunoglobin E (IgE), to attack and destroy the supposed enemy. Each IgE antibody specifically targets a particular allergen: the substance that triggers the allergic reaction. In this disease-fighting process, inflammatory chemicals, such as histamines, cytokines and leukotrienes, are released or produced and some unpleasant (and, in extreme cases, life-threatening) symptoms may be experienced by an allergy-prone person.

Approximately 15 percent of the population is allergic to animals.

What causes allergies to animals?

Animal fur does not cause animal allergies. Rather, allergy-triggering proteins found in animal dander (dead skin flakes), saliva and urine cause allergic reactions to animals. These proteins, called allergens, are either secreted by an animal's oil glands in its skin and shed as dander or are found in an animal's saliva and urine. When these proteins are shed or dry in animal fur, or become airborne, they can attach to carpeting, furniture and other objects and trigger allergies in people.

What animals cause allergies?

Household pets, such as dogs and cats, are the most common sources of animal allergens. But other furry or feathered animals, such as birds and rodents (hamsters, guinea pigs, gerbils, mice etc.), or livestock can cause allergy symptoms. "Non-allergenic" breeds of dogs and cats do not exist and even hairless breeds may cause allergies. Products made with feathers or down, like certain pillows and comforters, may also trigger allergy symptoms.

What are the symptoms of allergies?

An allergic reaction may occur in the skin, eyes, lining of the stomach, nose, sinuses, throat and lungs - places where immune system cells are located to fight off invaders that are inhaled, swallowed or come in contact with the skin. Reactions may result in the following:

• rhinitis - nasal stuffiness, sneezing, nasal itching, nasal discharge, itching in ears or roof of mouth.
• allergic conjunctivitis - red, itchy, watery eyes.
• atopic dermatitis - red, itchy, dry skin.
• urticaria - hives or itchy welts.
• contact dermatitis - itchy rash.
• asthma - airway problems such as shortness of breath, coughing, wheezing.

Who is affected by allergies?

Allergies can affect anyone, regardless of age, gender, race or socioeconomic status. Generally, allergies are more common in children, however, a first-time occurrence can happen at any age, or recur after many years of remission.

There is a tendency for allergies to occur in families, although the exact genetic factors that cause it are not yet understood. Often, the symptoms of allergies develop gradually over a period of time.

Allergy sufferers may become so accustomed to chronic symptoms such as sneezing, nasal congestion or wheezing, that they do not consider their symptoms to be unusual. Yet, with the help of an allergist, these symptoms can usually be prevented or controlled and quality of life greatly improved.

How are allergies diagnosed?

In addition to a complete medical history and physical examination, your child's physician may use the following:

• skin test - The skin test is a method of measuring the child's level of IgE antibodies to specific allergens. Using diluted solutions of specific allergens, the physician either injects your child with the solutions or applies them to a small scratch or puncture. Reaction appears as a small red area on the skin. A reaction to the skin test does not always mean that your child is allergic to the allergen that caused the reaction. Skin tests provide faster results and are more specific than blood tests.
• blood test - The blood test is used to measure the child's level of IgE antibodies to specific allergens. One common blood test is called RAST (radioallergosorbent test).

Medical treatments for allergies include immunotherapy (allergy shots), steroidal and antihistamine nose sprays and antihistamine pills.

Also, good housecleaning, such as frequent vacuuming, and using special air filters, pillows and coverings, can help create allergen-free or allergen-reduced environments. Sending pets outdoors more often, bathing and grooming them, and limiting the number of rooms they are permitted in can also reduce allergy symptoms.