What is an allergy?
Allergy, also known as hypersensitivity, is an altered immune response to a usually otherwise harmless substance. Children with allergies have increased sensitivity to one or more substances that ordinarily would be harmless in most people. Those affected by this sensitivity develop allergic responses when the substance is taken into the body through the nose, lungs, mouth or skin.
What is an allergen?
An allergen is any substance that can cause an allergic reaction. Some of the more common allergens are pollens, dust mites, mold spores, animals, and foods. An allergic response, or "reaction," is the result of how three factors interact: (1) the allergen, (2) mast cells (a type of cell found mostly in connective tissues) and (3) a protein called immunoglobulin E (IgE). Mast cells contain histamine and several other chemicals that cause itching, sneezing, watery eyes, swelling of tissues (inflammation), engorged blood vessels, increased secretions, and bronchospasm (tightening of the muscles that surround the airways).
When a child absorbs a particular allergen, the immune system manufactures immunoglobulin E (IgE) antibodies. IgE coats the surface of mast cells. When IgE antibodies react with an allergen on subsequent re-exposure, the mast cells release inflammatory chemicals into the body tissues. The effects of these chemicals on the tissues are what cause the symptoms of allergy.
What are the symptoms of allergy?
An allergic reaction can occur in almost any part of the body and the location of the reaction determines the symptoms produced. In the nose, symptoms include nasal itching, sneezing, stuffiness and runny nose. In the eye, symptoms include itching, tearing, redness and swelling. In the bronchial tubes within the lungs, asthmatic symptoms such as cough, wheezing, and difficulty breathing occur. In the skin, symptoms include rashes such as hives, and eczema. In the digestive tract, vomiting, abdominal pain, and diarrhea may occur.
Allergic reactions that occur in the nose, eyes, and bronchial tubes are usually caused by airborne allergens such as pollens, dust mites, molds, and animal danders. Allergic reactions that involve the skin and digestive tract are more often frequently caused by foods. However, in some instances, rashes can be caused by airborne allergens, and sudden episodes of wheezing can be triggered by foods.
Who gets allergies?
Allergies are quite common and occur in approximately 15% to 20% of all children. Allergies are a major cause of illness and missed school days in the pediatric population. Allergies are more common in boys under the age of 10, while girls between the ages of 10 and 20 are more likely to be affected.
What causes allergies?
Children are not born with an allergy, only the capacity to develop an allergy. Although all children are potentially allergic, certain individuals have an inherited predisposition for the development of allergies. Generally, a child becomes allergic after repeated exposure to an allergen, although occasionally an allergy may develop after only one exposure.
A child who has inherited the tendency to develop allergies may become sensitive to cow's milk shortly after birth, may become sensitive to cat dander at 6 years of age and after acquiring a cat, and throughout life may develop new allergies as exposures in the environment are encountered. These sensitivities or allergies may be life-long or may be eventually lost over time.
What is the relationship between allergies and asthma?
Asthma refers specifically to a reaction in the airways that may or may not involve allergy. Allergy is a reaction by the immune system that may or may not involve the airways. Substances that are airborne and capable of being inhaled are most likely to trigger asthma symptoms. Although only approximately 50% of adults with asthma have allergies, the majority of children with asthma have an allergy to one or more substances.
How are allergies diagnosed?
Allergies can be diagnosed in some cases by the patient's medical history and physical examination alone. Most children with allergies will require some type of testing to completely and precisely determine specific allergies. Testing is done either by a blood sample, or by allergy skin tests. Skin tests are usually performed in children by applying a drop of liquid allergen on the skin and then lightly pricking the skin's surface. In most cases, skin testing is preferable because it produces results within minutes, is highly accurate, and is less expensive than blood tests.
How are allergies treated?
The most effective treatment for allergies is the elimination of the trouble-causing allergens. For example, if the allergy is to a cat, dog, feather pillow, or food, the removal of the allergen should eliminate allergy symptoms. Allergies to plant pollens, mold spores, and dust mites can be partially avoided by decreasing exposure to the offending allergen, both inside and outside the home.
When avoidance measures fail to alleviate symptoms, medications may be helpful. Long-acting antihistamines, in addition to drugs that prevent and treat inflammation, are quite effective and produce minimal side effects. In some cases, allergy shots or allergen vaccines may be necessary to bring symptoms under control. Allergen vaccines contain extracts of the trouble-causing allergens and are designed to build up the body's tolerance to those allergens. The beneficial effects of allergy shots develop gradually, and it may take 6 to 12 months of receiving shots on a regular basis before any benefit is seen.
What research is being done on allergies?
Many studies are being done on the effects of allergies on overall health and lifestyle, as well as on ways to prevent and/or control allergies better. New medications are being developed that are more effective, longer acting, and have minimal side effects. Research is also being conducted on allergy vaccines that work faster and can be given at longer intervals than those currently being used.