Vaccination is the administration of specific weakened or killed antigens to stimulate the immune system so that the body will be protected against further exposure to the antigen. Vasculitis Vasculitis is an inflammation of the blood vessels. There are several types of the disease; they are classified according to the size of the vessels, the organ or organs involved, and the cause. The existence of an immunological mechanism of the immune-complex type has been demonstrated in some cases of vasculitis.

A mast cell is a type of tissue cell containing the chemical mediators responsible for the symptoms of allergy; when allergens attach to IgE antibodies lying on the surface of these cells, a signal is sent, causing them to release the chemical mediators of allergy.

Complications in the use of topical steroids occur in proportion to their potency, concentration, or fre­quency and duration of use. When complications do occur, they usu­ally take the form of burning sensations, irritation, itching, dryness, inflammation of the hair follicles, acne, loss of pigmentation, thinning of the skin, stretch marks, a tendency to bruise easily, dilated blood vessels in the skin, and skin ulcers. The risk of infection increases when the area treated is covered with a heavy dressing or a plastic wrap. Topical steroids should be avoided in cases of chicken pox and cowpox (vaccinia). The usual symptoms of scabies infestation (an easily transmitted skin disease, commonly known as mange and char­acterized by itching), as well as some fungal infections, may be ob­scured. Contact dermatitis can result when certain preservatives are used.

The bischromones, used primarily in treating allergic asthma and exercise-induced asthma, are sometimes used in treating patients with intrinsic asthma. Although bischromones can prevent symptoms of asthma, they should not be used to treat acute, or actively symp­tomatic, asthma, both because they do not dilate the air passages of the lungs, and because some bischromones are irritants. Bischromones have been tested for treatment of gastrointestinal allergy as well as some forms of inflammation of the lungs (pneu­monia) associated with allergic mechanisms. Dosages of the bischro-mone cromolyn, used in experimental work, have been as large as 400 milligrams (20 capsules) when taken orally four times a day. Avoiding the food that causes the allergy, however, is safer, simpler, more certain, and much less expensive. Use of the bischromones in studies of various allergic lung diseases has provided researchers with valuable information about the body’s immune mechanisms.

Rhinitis is inflammation of the nose. Allergic rhinitis occurs when an individual who is allergic to a foreign antigen, and who has anti­bodies against the antigen (bound to mast cells of the nasal mucosa), inhales the antigen. When antigen and tissue-bound antibody inter-react, mediators are released by the mast cells. These mediators cause dilatation of the blood vessels, leakage of fluid, and swelling of membranes, as well as increased production of mucus. Recent work has led to a clearer understanding of the mechanisms in the nasal pas­sages that control blood vessel constriction and dilatation. Research in recent years has clarified somewhat the mechanism of mucociliary clearance. Propelled by microscopic, hairlike protrusions called cilia, mucus continually cleanses the nasal membranes. Scientists know that many physiologic factors are involved. Methods of measuring changes in nasal airway resistance are being perfected, which means that the way in which foreign antigens affect the nasal passages should soon be better understood. Improved understanding of the allergens responsible for rhinitis is a research priority for the future, and the specific reactive parts of many antigens need to be defined. House dust, for example, is a mixture of poorly characterized components. The molecular identifica- tion of spores, pollen, and animal dander has just begun. Identification techniques must become more chemical-oriented. Which treatment methods cause the number of antigens to decrease? What is the optimal level of environment control? What are the most efficient and effective methods for removing danders, molds, and pollen from the environment? Someday allergy researchers will have to address themselves to these and similar questions. The treatment of allergic rhinitis pharmacologically is in the early stages as well. Medications that compete with the mediator histamine at the histamine receptor sites of the nasal mucosa are known as antihistamines. Decongestants are used systematically and topically to shrink blood vessels and thereby decrease fluid leakage and the swelling of membranes. Although effective only for brief periods, topical agents, if overused, can aggravate the nasal mem­brane swelling already underway. Each of the six families of anti­histamine has a different, fundamental chemical structure. If a drug from one family is ineffective in a particular patient, a drug from another family may be tried and found effective. The best-known side effects of antihistamines are drowsiness, dryness of the mouth, and blurred vision. Sometimes combinations of systemic decongestants and antihistamines are used with good results. Topical corticosteroid sprays are a potent adjunct for more serious cases of rhinitis. They are commonly used for brief periods, however, since some degree of systemic absorption occurs, and adrenal gland suppression, a con­sequence of corticosteroids usage, is a potential adverse effect. The modification of allergic rhinitis by medication is still of un­certain value. Scientists as yet know little of the relationship of dosage to response for either decongestants or antihistamines. Physicians prescribe the drags at dosage levels that appear to relieve distress without adverse effects, but neither they nor scientists have determined the optimal dosage for a given individual. Finally, the development of tolerance to these drugs and how long topical corti­costeroids can be used safely are still a mystery.

Rinkel desensitization is an unproven and controversial method of allergy desensitization involving "end point" titration skin testing. In this technique the amount of allergen given during desensitization is based on quantitative skin testing. A recent controlled double-blind study performed by highly qualified allergists at the Johns Hopkins Medical School has shown this method of treatment to be ineffective, in that it was no better than placebo (an inactive substance used in well-controlled clinical trials) in treating allergic rhinitis.

Gastroenteritis is an inflammation of the stomach and intestines. It may at times result from an allergic reaction.

Below is a selected list of companies that manufacture food prod­ucts for restricted diets, including diets prescribed by doctors for allergic patients. (Check with your doctor first, however, to determine if these products are suitable for your or your child’s particular, special diet.) When searching for a particular product, call up your local super­market to see if it is in stock. If that store does not have the product you want, the store manager may be able to refer you to another supermarket or grocery store in the area that does.