CHILDREN’S ALLERGIES: SKIN TESTING

If a child is suspected of having allergies, a confirmation is possible through the following means: an allergic history, a physical examination, laboratory tests, a study of the environment, and a diet evaluation. When this workup points toward an allergy, skin tests and a Rast reaction test will detect the cause or causes of the disease.

The Allergic History

An allergic history should be taken by the child’s doctor and should include:

Name

Address

Chief complaint

Family history of allergies

Infectious and contagious diseases

Immunizing procedures and reactions

Pets in the house

Bedding (covers, blankets, mattresses, sheets, etc.)

Nose and throat infections (colds, tonsillitis)

Food idiosyncrasies

Present illness:

Initial attack

Subsequent attacks

Last attack

Tentative diagnosis

http://drugswatcher.com/product_info.php?cPath=50&products_id=2290Skin testing

Once the allergic history and other standard workup procedures are completed, skin testing is begun. This involves the provocation of an allergic reaction in the skin through exposure to a minute amount of an allergen. It is the easiest and simplest method of detecting sensitivity to an inhalant allergen, but it has little value unless the above-mentioned studies point to it.

One method of skin testing is to first prick or scratch the surface of the skin and then put an allergenic extract on the abraded area. Another method (intradermal) is to introduce, with a needle, a small quantity of an allergenic extract between the layers of the skin. A third method (used to detect the cause of contact eczema) is the patch test, which places a piece of gauze soaked in the suspected allergen on the skin for a prolonged period of time. A fourth method, rarely used now, is the conjunctival test, performed by putting a drop of an allergenic extract in the eye.

All these tests may be performed before, while, or after allergy symptoms are present. However, some drugs used to control allergies, such as antihistamines, adrenalin, aminophylline, atropine, and ephedrine, may reduce the intensity of the skin’s reaction to the test. These drugs should be discontinued forty-eight hours before any skin test is performed. (Cortisone, on the other hand, even though very effective for allergies, has no effect on a skin test.)

The skin of the inside of the arm is used for scratch or intradermal tests because the arm allows the use of a tourniquet in case of a severe reaction to testing. To perform scratch tests, a small scalpel which can make an incision in the skin (without drawing blood from it) is used. The skin site is cleaned with alcohol, ten scarifications are made, and a small amount of an allergen extract is placed over each scarification. To perform intradermal tests, the skin site is cleaned with alcohol, a different allergenic extract is put into each one of ten disposable allergy syringes, and an injection of 0.02 cc. of each extract is made between the layers of the skin.

After performing skin tests, an “immediate” reaction may appear after fifteen minutes, or a “delayed” reaction may appear ten to fifteen hours later. (Delayed reactions are known to occur when testing for molds.) These tests are read differently by different allergists. Some doctors consider that:

a. A slight skin reaction is a one-plus reaction.

b. A moderate reaction is a two-plus reaction. ñ A marked reaction in a three-plus reaction.

d. A marked active reaction (or one with “branching” feet) is a four-plus reaction.

Others use a mathematical way of reading the tests, depending on the size of the wheal:

a. 1/2 cm. is considered a one-plus reaction.

b. 1 cm. is considered a two-plus reaction.

ñ 1 1/2 cm. is considered a three-plus reaction, d. 2 cm. is considered a four-plus reaction.

Still others prefer to measure the intensity of a reaction according to the size of a standard circle:

a. A wheal as large as the head of a pin is a one-plus reaction.

b. A wheal as large as a dime is a two-plus reaction.

ñ A wheal as large as a nickel is a three-plus reaction.

d. A wheal as large as a quarter is a four-plus reaction.