What is an allergy?
An allergy is an abnormal reaction to an ordinarily harmless substance or substances. This abnormal reaction occurs because the allergic immune system specifically recognizes the substance, and physiological changes occur in certain parts of the body when the allergic immune system comes in contact with the substance. These substances, called allergens, may be inhaled, swallowed, injected or come in contact with the skin. Pollens, molds, house dust, animal dander, medicines and insect venom are among the most common allergens.
No one knows exactly why some persons have allergies, while other do not, but evidence shows that heredity is an important factor in their development. When an allergy-prone individual is first exposed to a particular allergen, he or she produces a protein called IgE antibody, a specific kind of antibody responsible for allergies. (Other antibodies protect the body by helping to fight off and destroy foreign invaders, such as bacteria and viruses.) The IgE antibodies attach to the surfaces of two types of cells known as mast cells and basophils. Mast cells are found primarily in the respiratory and digestive tracts and the skin. Basophils are found in the blood.
When an allergic person again encounters the allergen, it binds to the IgE antibodies that are already on the mast cell or basophil cell surface. However, each antibody reacts with the specific allergen against which it was made. The combining of the allergen with it antibody is a signal to these cells to release chemicals, known as mediators, that cause the various allergic symptoms, such as wheezing, sneezing, hives and abdominal pain. One of these chemicals is histamine which is why antihistamines are useful in controlling allergic symptoms.
What are the allergic diseases?
Allergic diseases or reactions may involve any part or system of the body. Most frequently affected are the respiratory system resulting in hay fever, rhinitis and asthma, and the skin, which develops allergic dermatitis (atopic eczema), hives (urticaria) or contact dermatitis (poison ivy). Allergic factors may also play a role in the cause of some other diseases.
Allergic rhinitis is a general term used to apply to anyone who has nasal congestion, sneezing and a runny nose due to allergies. This may be a seasonal problem as with hay fever (described below) or it may be a year-round problem caused by allergens such as house dust or animal danders. Frequently this problem is complicated by "sinusitis"; therefore, most patients with constant nasal symptoms should have an allergy evaluation.
Hay fever is a form of allergic rhinitis. The name is actually a misnomer, since hay is not a common allergen and no fever occurs. It was a term established by English physicians caring for patients with allergic nasal symptoms during the "haying season" of late August and September. Classic hay fever (fall symptoms) is usually caused by ragweed pollen as this is the major fall pollen allergen. However the term, hay fever, has been used for any form of weeds as well as the spores of molds. Depending on the section of the country and the pollinating periods, the hay fever may occur in the spring, summer, fall and may last until frost. The sufferer has spells of sneezing, itching and weeping eyes, runny nose, burning palate and throat. Asthma is sometimes a complication.
Asthmais a condition characterized by chest "tightness", coughing, wheezing and difficulty breathing. It is frequently, but not invariably, associated with a family history of allergy. Any of the above-mentioned allergens may cause asthmatic attacks. Infections of the sinuses or bronchial tubes may also be important factors. Patients with asthma are also affected adversely by many so-called non-specific factors such as air pollutants, cigarette smoke, fumes, etc., and at times by emotional reactions. No psychological process has been clearly established as a cause of asthma. Asthma may begin at any age. Adult onset asthma tends to reoccur and become chronic.
Atopic allergic dermatitis or eczema is a non-contagious, itchy rash that often occurs in the creases of the arms, legs, and neck, although it can cover the entire body. This condition is frequently associated with an allergic genetic predisposition and other forms of allergy symptoms. Foods may be important causes of this problem in approximately 25% of children who suffer from eczema.
Pulmonary Function Test: When the diagnosis is asthma, the doctor often wants to know exactly how well the lungs are functioning. Lung (pulmonary) function tests may be performed, using various instruments. These tests will help the doctor learn the severity of the asthma. Later tests can be compared with the first tests to see how well your treatment program is progressing. Lung function tests can tell the doctor how much air your lungs can hold, how much you can breathe out, how much air remains trapped in your lungs and how constricted your breathing tubes are. Most of these tests have technical-sounding names, which your doctor can explain if they are given.
Elimination Diet:Because skin testing alone cannot reliably be used to diagnose food allergies, particularly in children, a carefully controlled diet, called an elimination diet may also be used. In this "test", certain foods suspected of causing allergy are left out of the diet for a while and then added back one at a time to see if symptoms redevelop. If symptoms do occur, the last food that was added to the diet is eliminated until symptoms disappear, and the food is tried again. If symptoms reappear, the person is probably allergic to that food. An elimination diet may start with only a small number of foods that seldom cause allergies. Or a more normal diet may be used, which limits only the most common food offenders at first.
What is the treatment for allergic disease?
Three approaches are used in treating allergies. In some cases, only one treatment approach may be needed, while in other situations the doctor may recommend all three.
- Avoidance of Allergen: Allergens should be removed from the patient's environment. This is relatively easy if feather pillows or other dust-catching furniture are the problems. However, if there is sensitivity to a pet, such as a cat, dog or bird, it is not always simple to remove because of the emotional attachments involved. It can be done; however, with patients, compassion and careful explanations of the dangers of continued close contact. At the very least, pets should be kept out of the patient's bedroom. While dust and molds are harder to avoid, steps can be taken to reduce their levels at home.
- Medications: The proper use and timing of medications is important in treating allergic disease. The doctor must determine the particular ones and their dosage. There are now numerous medications which are helpful in prevention and for providing relief of symptoms. This may be all that is needed in mild allergy cases. If you experience any significant side effects from your medicine, you should report them to the doctor right away. If symptoms persist, despite the proper use of medications and the removal of allergens from the environment, then immunizing injections (immunotherapy) may be necessary to control the disease.
- Immunotherapy: This form of treatment is also called desensitization, hyposensitization, or "allergy shots". Immunotherapy is used in the treatment of allergic patients with respiratory symptoms, mainly of hay fever or asthma. In this form of treatment, injections of allergenic extract are given in gradually increasing amounts over a period of months. The goal is to induce a degree of tolerance to the allergens and to bring about a decline in the symptoms and the medication requirements. The specific schedule for injections and the amount of extract to be given vary from patient to patient. Just how long you must continue the shots cannot be predicted, but most patients get them at least three years. Usually shots are given for at least two years after symptoms significantly decrease. In general, the doctor tries to increase to the maximum dose that can be tolerated without reaction.
You will be asked to remain in the office for 20 minutes after the injection to be sure that there is no systemic reaction. Early signs of a reaction include itching of the neck and palms and a feeling of uneasiness. Fortunately, such reactions are rare. When they do occur, they can be brought under control quickly with medication. Slight swelling frequently occurs where the injection was made, but this usually goes away in a few hours.
Unit the shots become effective or when shots are not desired, medicines are given to control unpleasant symptoms. These, of course, act only temporarily and will not get rid of the allergy on a permanent basis.
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