Allergy is the body's response to the presence of some aggravating agent called an allergen. Individuals act differently in their responses to allergens; therefore some people are more allergic than others.
It used to be assumed that all allergens were protein substances, and it was common to speak of "protein sensitivity." It is known that some allergens are carbohydrates, and at least a few are chemically related to the fats. All allergens have one thing in common - they stimulate a sensitive person to react by producing antibodies.
The allergic reaction results from intricate chemical processes, such as enzyme reactions, and is related to the processes by which immunity is developed. Becoming immune to a certain germ whose products have served as an allergen is one form of allergic response. When the antibodies which a certain allergen produces are stationary within a group of the body's cells rather than being free in the bloodstream, then these cells in which the antibodies are located may be unfavorably affected when exposed to this specific allergen.
Kinds of Allergen
1. Some allergens enter the body by being inhaled. These include pollens; dusts; vapors, such as tobacco smoke; emanations such as dandruff; and strong odors such as perfumes (dust allergy, nasal allergy).
2. Certain foods provoke as allergic response in sensitive persons. These include wheat, milk, chocolate, eggs, strawberries, nuts, pork, and fish (wheat allergy, strawberry allergy, fish allergy, egg allergy, food allergy).
3. Some persons become sensitive to drugs or biological agents. These, then, can serve as allergens (drug allergy).
4. Certain germs may function as allergens. The symptoms produced when these germs invade a person's tissues are the result of the allergic response.
5. They are allergens which cause the allergic response through a mere contact with the skin or mucous membranes of a sensitive person. These include products from plants such as poison oak and poison ivy, and certain dyes, metals, plastics, furs, leathers, rubber products, cosmetics, and chemicals such as insecticides (skin allergies, cat allergy, dog allergy).
6. Even physical agents such as heat, cold, light, and pressure may cause an allergic response. Many a hay-fever sufferer begins to sneeze when he steps into bright sunlight.
Preventing the Allergic Response
In general, there are four ways to prevent or modify allergic symptoms.
A. Avoiding the allergen. The simplest way to avoid allergic response is to keep offending allergens from entering the body. Hay-fever sufferers can often prevent their attacks by staying indoors during the time of year when certain plants bloom. If these plants are limited to a certain locality, the sufferers can avoid symptoms by staying away from this locality. Allergy to a drug can be avoided by not using the drug. Allergy to some food may be handled by excluding this food from the diet. Persons sensitive to a particular dust may wear a filtering mask. Air-conditioning systems with air filters often bring relief to hay-fever and asthma sufferers.
B. Desensitization.It is possible to build up a person's tolerance to most allergens by administering gradually increasing doses of this allergen. Physicians can obtain preparations of the usual allergens from medical supply houses and can inject these into a sensitive patient, beginning with very small doses and building up until the patient's tolerance has improved to where he no longer develops symptoms when exposed to the allergen. This method has proved quite successful for many patients suffering from hay fever and some types of asthma.
C. Antihistamines.In many cases of allergy, the body's tissues liberate histamine in response to the presence of an allergen. An antihistamine drug may relieve this allergic response. There are many varieties of these medications. One kind will benefit some allergic persons and another kind, others. It may be necessary to use the trial-and-error method to determine which antihistamine will bring the greatest benefit.
There is some hazard involved in the use of antihistamine drugs; many of them have the side effect of making a person drowsy. It is dangerous, therefore, for the person taking such drugs to drive a car.
D. Hormones. In cases of extremely serious allergic reactions, the use of steroid preparations may provide some benefit. These powerful medicinal agents should be used only under the supervision of a physician.
HAY FEVER
The symptoms of this illness depend typically upon an allergic response to an offending protein substance breathed in with the air.
ASTHMA
At least half the causes of asthma seem to be caused or aggravated by allergy.
HIVES (URTICARIA)
This skin manifestation usually results from an allergic response to some offending allergen.
ANGIONEUROTIC EDEMA
This manifestation of the allergic response involves the skin in much the same manner as in hives except that here we have one or more large swollen skin areas. In some forms of the disease, this area of swelling may involve the lining of the larynx so as to interfere with breathing and even endanger the victim's life. In other cases it is the face, hands, feet, and genitalia that become swollen.
SERUM SICKNESS
Serum sickness is an allergic reaction triggered by the injection of a serum of animal origin (usually horse serum). Certain antitoxins, valuable in the treatment of specific infections, are contained in animal serum. This allergic reaction typically occurs in persons who have had a previous injection of this same kind of serum and have become sensitive to it. Because of this possibility physicians prefer to use toxoid preparations, when available, rather than the antiserums.
Symptoms of serum sickness may develop as long as fourteen days after the injection. However, they may occur more promptly in previously sensitized persons. The illness begins with a skin eruption resembling hives. There is fever, enlargement of the lymph nodes, pain in the joints, nausea, and abdominal pain.
Emergency treatment for serum sickness requires the use of carefully graduated small injections of a 1:1000 solution of epinephrine. Usually the beginning injection consists of.5 ml. of this dilute solution. It is followed a few minutes later by an injection of 1 ml. depending upon the patient's condition; the injection may need to be repeated two or three times at intervals of a few minutes.
DRUG ALLERGY
An allergic reaction may occur in sensitive individuals after the taking of certain drugs. There are said to be more than one hundred drugs which provoke an allergic response in sensitive persons. Notable offenders are the sulfonamides and penicillin.
Development of a skin rash is the usual manifestation of a drug allergy. Fever and symptoms of shock may occur in extreme cases. Discontinuance of the offending drug is the obvious treatment, the symptoms usually disappearing soon after the drug is discontinued.
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