Allergy is today considered as the sixth chronic illness that affects a large population of adults and children in the United States. The symptoms of allergy make daily life, difficult and hard to deal with.
It is best to check for allergies when the symptoms have just started to show. An allergy test is done to understand how a body reacts to specific allergens like pollen, foods, medications or molds. If the test is positive, the person has the allergic antibody to that substance where he will experience symptoms when exposed to that allergen. However this positive result need not necessarily mean that he is allergic to that allergen. It is thus important for an allergist to carry out and analyze the test results based on the symptoms exhibited.
The commonly used tests are - prick test, patch test, oral and blood test.
Patch Test
This test is done to check if the person has eczema or contact dermatitis. The allergens are applied on the skin for a specific period of time. For contact dermatitis the allergens are left for half an hour on the skin. If the area gets red, itchy and swollen the test is positive and the allergen is the causative factor. If the symptoms show atopic dermatitis the allergens are left for a longer period on the skin say up to 48 hours to test for blisters, swelling, redness and crust formation.
Prick Test
This is the oldest and most suitable form of testing and has been around for over 100 years. The allergen is placed on the skin after a prick, puncture or a scratch with a needle. The skin is checked after 15 minutes for results. This skin test may be performed based on the person’s age, symptoms and other factors. A positive test indicates red itchy swelling similar to a mosquito bite. The test conducted is compared to the positive and negative controls. The positive control is histamine which is reliable to rule out any negative tests. The negative control used is salt water to ensure that any irritant feeling is not due to the pricking of the needle.
If the test is negative for a person with a history of allergies an intradermal skin test can be performed. In this test the diluted allergen is injected under the skin layer. This unfortunately is a not a very reliable test as it can give false results. In cases where the skin test cannot be performed the antibody production against an allergen can be checked from the blood sample.
Blood Tests
RAST (radioallegosorbent test) helps to check the amount of antibodies to a specific allergen. If the levels are high then the person has allergies. However, raised or normal levels do not truly indicate that you are allergic.
Skin tests usually give less false positive and negative results.
Oral Tests
This test is done if the doctor is not able to conclude with any of the above test results. A small quantity of the suspected food is taken and the symptoms are recorded. After a gap of 30-60 minutes, a second intake of larger quantity of the same food is given to read the symptoms. If any symptoms develop during the tests then that food is identified as the causative factor.
Treatment
There are a number of drug treatments given to combat the action or counteract the effect of histamine in allergic reactions.
Antihistamines
These prevent the histamine from affecting the cells and tissues. Some drugs which can cause drowsiness as side effect are chlropheniramine, brompherniramine, diphenhydramine and clemastine. The drug terfenadine has no drowsiness effect.
Topical Corticosteroids
They are applied directly on the skin to reduce inflammation on mucous membranes and tissues around the nose and mouth. The drugs provide protection throughout the period of an allergic reaction.
Decongestants
These constrict the blood vessels and thereby reduce swelling, redness and itching caused by histamine. They can be taken in the form of pills or nose sprays.
Immunotherapy
This is the form of desensitization where injections are given for long time periods to reduce the action of antibodies that cause allergic reactions.
Bronchodilators
These help to dilate the airways to let air flow through easily. This enables the person to breathe without discomfort. These dilators are used during asthmatic attacks and can be used as sprays through nose or throat.