Allergies are physiological reactions caused when the immune system reacts to a foreign substance (allergen) that has been inhaled, touched, or eaten by a person.
Normally, the human body defends itself against harmful substances, such as viruses or bacteria, but, sometimes, the defenses aggressively attack usually harmless substances such as dust, mold, or pollen.
The immune system makes large amounts of the antibodies called immunoglobin E (IgE), to attack and destroy the supposed enemy. Each IgE antibody 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.
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:
Seasonal or allergic rhinitis (nasal stuffiness, sneezing, nasal itching, nasal discharge, itching in ears or roof of mouth)
Allergic conjunctivitis (red, itchy, watery eyes)
Atopic dermatitis or eczema (red, itchy, dry skin)
Urticaria (hives or itchy welts)
Contact dermatitis (itchy rash)
Asthma (airway problems, such as shortness of breath, coughing, wheezing)
Although hundreds of ordinary substances could trigger allergic reactions, the most common triggers, called allergens, include the following:
Tree, grass, and weed pollens
Natural rubber latex (protein)
Animal protein (dander, urine, oil from skin)
Cockroach droppings and body parts
Allergies can affect anyone. Generally, they are more common in children. However, a first-time occurrence can happen at any age, or recur after many years of remission.
There's a tendency for allergies to occur in families, although the exact genetic factors that cause it aren't yet understood. Often, the symptoms of allergies develop gradually over time.
Allergy sufferers may become used 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.
In addition to a complete medical history and physical exam, your child's doctor 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, an allergist pricks the surface of the skin with these solutions on plastic prongs. A reaction to the skin test doesn't always mean that your child is allergic to the allergen that caused the reaction. Skin tests provide faster results, typically taking 15 minutes, 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).
Challenge test. This is a test supervised by an allergist because a very small amount of allergen is taken by mouth or inhaled.
Your child's doctor will consider your child's age, overall health, and other factors when advising the best treatment. Medications can help lessen allergy symptoms. In some cases, allergy shots are needed. This involves injecting small amounts of the allergic substances. This stimulated the immune system to fight the allergy. Allergy shots are usually needed weekly for a time, then every few weeks and are given by an allergist.