Allergy Skin Testing

Diagnosis and treatment of patients with allergies

In addition to history taking and physical examination, Allergy testing should also be performed to determine which substances the patient is allergic to. This may be done through blood tests, nasal tests (in the case of allergic rhinitis) or skin tests. In general, skin testing is preferred as it is quick, easy, giving immediate results at less cost.

 

Benefit of allergy skin testing

In addition to medicine taking, principles of looking at and treating allergy patients is to avoid of allergens contact. However, there are many allergens surrounding us which is difficult to avoid them at all time. But if we know which substances we are allergic to and avoid them directly, it will improve the treatment results. In addition, all patients requiring allergy vaccination treatment. It is necessary to undergo an allergy test first to see if you are allergic to any substance in order to be treated with an appropriate solution prior to the substance that the they are allergic to.

From what age can you take the test?

           In general, it can be tested at any age. But young children ( with less than 6 months) and in the elderly may give a false negative result because the sensitivity of the skin is less.

 

Preparation before the test

     1. Refrain from antihistamines for 7 days prior to the test.

     2. for those who took some medications may contain antihistamines, such as cold medications, nasal decongestants, anti-itch medications, must be abstained 7 days prior to the test.

     3. Patients with heart disease, hypertension, should mention the name of the drug you are taking to the doctor who will be testing because some drugs must be stopped before the test.

     4. Topical steroids may suppress the result which should be abstrained prior to the test as well.

     5. Do not need to withhold water and food before taking the test.

 

Test Reagent

          They are the the purified extract from allergens, for example, dust mite extracts. Hair and dandruff of animals such as dogs, cats, horses, rabbits, ducks, chickens, geese, birds Debris of insects in the house such as cockroaches, flies, fungi plant pollen such as weeds, ferns, perennials, grasses Foods such as cow's milk, eggs, nuts, meat, seafood, vegetables and fruits some kind. It must be a solution that has a standardized production process. Each substance are separated into different bottles. It provides reliable test results. Different types of reagents can be used at a differ amount depending on the age and history of each patient.

 

There are 2 types of test

1. Skin Prick Test (SPT)

Dropping an allergen on the patient's skin using a needle to poke gently through droplets and within the epidermis (no bleeding) then wipe off the solution and wait for 15 minutes for the results. If the patient is allergic to any substance, red bumps caused will be detected on the tested spot of that substance. Nowadays, plastic rods with a pointed fork-like tip (Duotip) are used instead of needles, dipping the solution and then poke it on the patient's skin without a single drop of the drug which make it easier to be used. SPT is widely accepted and recommended for skin testing diagnosis of allergies because it is a safe way, less likely to cause severe allergic reactions, easy to do, less time required, the solution does not need to be diluted thus makes the solution more durable and more time correlated with clinical symptoms comparing to intradermal skin test.

 

2. Intradermal Skin Test (IKT)

          This method is done by injecting an allergen solution into the skin and wait for 15 minutes until the results show up. The disadvantage of this method is that patients, especially children, are found to be less cooperative during the test as it can cause pain. Moreover, the side effects like severe allergic reactions may occur more often as many substances are injected into the body, especially in patients who took certain medications (which is generally very rare, < 1%). However, the test should not be performed in patients with severe symptoms such as severe asthma, itching at the test spot occurs frequently and may resolve on its own or by taking antihistamines.

 

Best wishes from

Pediatric Clinic, Vibhavadi Hospital (Outpatient) Tel. 0-2561-1111 , 0-2941-2800 press 1 Check-up time 07.00 – 20.00