Allergies are abnormal reactions to ordinarily harmless substances. The sensitizing substances, called allergens, may be inhaled, swallowed, or come into contact with the skin. Allergens that most frequently cause problems are: pollens, mold spores, house dust mites, animal danders, foods, insect bites or stings, plants, insect spores, latex rubber, viruses, bacteria, medications and environmental conditions (such as cold temperatures). Allergic reactions can occur in one area, such as sneezing or a skin rash or sneezing, or may include more than one symptom.
Normally, the body learns to defend itself through experience - by encountering, battling and remembering one enemy after another. For decades, medical science has taken advantage of this ability by using vaccination to create immunity - the immunologic "memory" of a disease. Allergic reactions occur after the immune system mistakenly learns to recognize innocent foreign substances (allergens) as potentially harmful. The following story illustrates how an allergy can develop:
Over a field of ragweed plants floats an invisible cloud of pollen grains, soon carried by the wind into a nearby town. The pollen is inhaled by a child whose body has never been exposed to this substance before. Because of some genetic predisposing factor, this child's immune system overreacts and produces large numbers of IgE antibodies, all specially designed to respond to ragweed pollen. Several of the antibodies attach themselves to cells in the child's nasal passages and upper respiratory tract. These cells (known as mast cells) contain strong chemicals called mediators, the best-known of which is histamine. Later, when the child inhales the same kind of pollen again, proteins from the pollen bind in a lock-and-key fashion to the specially designed antibodies on the surface of the mast cells. This sets off an explosion of sorts, as the mediators burst from inside the mast cells, destroying the pollen and also damaging surrounding tissues. The results are sneezing, a stuffy head, sniffling, stuffed-up head and red, watery eyes - well-known hallmarks of allergies.
The fundamental cause of allergy is still not known. The problem has a tendency to run in families. An allergic individual is more likely to have relatives who are allergic than would be expected on the basis of chance, but non-hereditary factors apparently play a part as well. Evidence of this is the fact that infants who are breast-fed are less likely to develop allergies than bottle-fed babies. The reason an individual becomes sensitive to some substances and not to others remains a mystery. Individuals can be affected by a variety of allergic diseases. The most common allergic diseases are allergic rhinitis, non-allergic rhinitis, asthma, allergic dermatitis, contact dermatitis and urticaria. (Allergic rhinitis is the most common of the allergic diseases and the main focus of this health profile. More comprehensive information about the other conditions may be found under that particular term.) Allergic rhinitis is a general term used to apply to anyone who has allergy-based symptoms. Allergic rhinitis can be a seasonal problem (commonly known as "hay fever" or pollen allergy) or a year-round problem (commonly known as perennial allergic rhinitis). Hay fever or seasonal allergic rhinitis is caused by allergy to pollens of trees, grasses, weeds or mold spores. Perennial allergic rhinitis is caused by house dust, animal danders, mold and some foods. Asthma is caused by intrinsic and extrinsic (inhaled) factors. Intrinsic factors are pollens, dust, dust mites, animal fur, animal dander or feathers. Extrinsic factors are respiratory infections; a cough, cold or bronchitis; exercise and tobacco smoke or other air pollutants, and can be caused by an allergy to a particular food or medication. Allergic dermatitis, also known as "eczema", can be caused by foods or other allergens. Contact dermatitis is caused by exposure to certain plants (such as poison ivy or poison oak), cosmetics, medications, metals and chemicals. Urticaria, also known as "hives", is caused by allergy to foods, such as nuts, tomatoes, shellfish and berries. Hives can also be caused by medications, such as aspirin and penicillin.
The signs and symptoms of allergic rhinitis are:
The signs and symptoms of asthma are:
The signs and symptoms of allergic dermatitis, contact dermatitis and urticaria are:
WARNING: If a person is experiencing more severe symptoms than what is listed above, they may be in anaphylactic shock. Anaphylactic shock is a medical emergency which is an acute systemic (affecting the whole body) allergic reaction. It occurs after exposure to an antigen (allergen) to which a person was previously sensitized. The signs and symptoms of anaphylactic shock include the general symptoms of a common allergic reaction, PLUS:
Allergens more commonly associated with anaphylactic shock are: certain insect venoms; drugs such as penicillin; and foods like fish, peanuts, nuts, eggs and seeds. Call 911 if any of these symptoms occur with an allergic reaction. If not treated promptly and properly, anaphylaxis can result in death. Fortunately, the tendency to have such serious reactions is rare. Treatment of anaphylactic shock is first to inject adrenaline (epinephrine) to constrict the small blood vessels, raise the blood pressure and dilate the airway. This may be followed by injection of antihistamines and/or steroids, plus the use of life-support systems.
Besides a thorough medical history, the doctor will perform a number of skin tests and/or a blood test called radioallergosorbent test (RAST). There are three skin tests used to evaluate and diagnose allergies, the prick method, the intradermal test and the patch test:
When skin testing is not feasible, as in the case of people with eczema and other skin conditions, RAST (blood test) is used. Diagnostic tests can be done by using a blood sample from a patient to detect the levels of IgE antibody to a particular allergen.
There are three general approaches to the treatment of allergic diseases such as allergic rhinitis: avoidance of the allergen, medication to relieve symptoms and allergy shots. Avoidance
Medication When avoidance or control of an allergen isn't possible, medications may be necessary. Common allergy medications are:
Immunotherapy When avoidance, environmental control measures and medications fail to control allergy symptoms, the doctor may suggest allergy immunotherapy ("allergy shots"). Immunotherapy involves the injections of allergen extracts to "desensitize" the person. Typically, the treatment begins with injections of a weal solution of allergen given one to five times a week, with the strength gradually increasing. When the maximum dose is reached, maintenance injections are given at increasing intervals until the patient receives injections only once a month. It may take up to six months or so to show results. It usually takes about three to four years for the patient to be free of symptoms. Treatment of Asthma Asthma treatment involves agents that relax the airways. These agents include beta-adrenergic agonists, theophylline, anti-cholinergics and occasionally expectorants and mucolytics. Treatment of Allergic Dermatitis, Contact Dermatitis and Urticaria Eczema (allergic dermatitis) and contact dermatitis (such as with poison oak or ivy) can be treated with cold compresses for 30 minutes 3 times a day, and/or corticosteroid creams or ointments (topical steroids). Hives (urticaria) can be relieved by applying calamine lotion or by taking type H1 antihistamine drugs. More severe cases of hives may require corticosteroid drugs.
Should skin testing be done? Do you recommend nasal sprays or drops? What are the side effects? What other medications are recommended to relieve the symptoms of allergies? Do you recommend desensitization with injections? What measures can be taken minimize the reactions? Do allergic rhinitis (hayfever) reactions lead to sinus infections or asthma or any other condition? Are foods causing the allergies? Am I at risk for anaphylactic shock? If so, what precautions can I take?