Allergy test plays pivotal role in Allergy diagnosis and treatment.Allergy Tests are used to confirm clinical sensitivity induced by aero allergens, foods, some drugs, a few chemicals, and hymenoptera venom.
What are the various Allergy tests available?
Allergy test can be broadly divided into two groups-
1.Allergy Blood test
2. Allergy prick test
Allergy Prick Test- In Allergy prick testing small quantity of allergen is introduced through the patient’s skin and results are seen in the form of wheal flare reaction in 10 to 20 minutes.Skin prick testing can be performed by various methods for example Intradermal test,Scratch test and modified skin prick test.
Modified prick testing method is most commonly used by the Allergists all over the world. In comparison with other methods it is least painful,safe and accurate
What are the indications of allergy test?
Allergy test is advised in the following disease conditions-
- Allergic Rhinitis
- Food Allergy
- Atopic dermatitis
- Hymenoptera ( Insect bite) hypersensitivity
Is there any factor that can affect Allergy prick testing results?
- Intake of oral anti histamine (for ex cetrizine,levocetrizine,Allergra,desloratidin etc and some antidepressants) within a week of Allergy test can give false negative results.So that patient is advised to withdraw antiallergic medicines at least a week before the test.
- Local use of steroid cream at the site of allergy prick testing for example forearm and back alter the allergy test results.
- Age-infancy or old age
- Sex -no difference
- Race-wheeling more in blacks
- Circadian rhythm peak in late evening
- Seasonal variation pollen allergy
- Skin condition-skin eczema
- Other condition-diabetic neuropahthy
*Skin test can be performed even at one month of age
SPT is a simple, safe and quick test, providing results within 15-20 minutes. This will enable you to receive a diagnosis and management plan at your appointment.
Skin prick testing is done demonstrates an allergic response to a specific allergen. SPT can help to confirm the presence of an allergy to pollen, food, dust, mites, moulds and animal dander’s.
The skin prick test introduces a tiny amount of allergen into the skin, eliciting a small, localized allergic response, in the form of a wheal (bump) and flare (redness) at the site of testing. These tests can be carried out on all age groups, including babies. The test allergens are selected following a discussion with your clinician and based on your history.
The patient needs to avoid taking anti-histamines and certain other medications before the test.
Antihistamine for example cetrizine,loratidine,fexofenadine should stop at least 5 to 7 days before the testing
Tricyclic anti depressant ( doxepine)and atypical antipsychotic drugs (ex.risperidone,olanzapine,ziprasidone) should be taper down if required a wk before the testing.
Beta blockers should be stopped in all instances 24 hour before the testing
Potential Risks of Non-Specialist Care
- Misinterpretation of test results
- Over diagnosis
- Over prescription of medications and treatments
- Costly and unnecessary allergen avoidance measures
Medications and the period of abstinence before SPT
- First generation short acting Antihistamines (Anti allergic) should be stopped three days before the testing- Avil(Pheniramine),Chlorpheniramine,Phenergan(Promethazine),Benadryl(Diphenhydramine),Cinnarizine,Meclizine and Cyclizine
- First generation long acting H1Blocker should be stopped 7 days before the prick testing- Atarax (Hydroxyzine)
- Second generation long acting H1 blocker -Should be stopped 7 days before the testing- cetrizine,levocetrizine,loratidine,desloratidine,ebastine,mizolastine,bepostatine
- Second generation long acting H1 Blocker-Should be stopped 5 days before the testing- Fexofenadine,Polaramine
- Second generation short acting H1 blocker – Azelastin And olapatadine
- Second generation long acting H1 blocker Cyproheptadine and ketotofen should be stopped for 14 days
- Topical steroid -21 days
- Topical antihistamine ointment or cream – 7days
- Topical calcineurin inhibitors -7 days
- Depot steroid Kenacort,Depomedrol- 90 days
- Short term oral prednisolone or equivalent >40 mg/d -equivalent for 7 days or more
- Short term oral prednisolone or equivalent 30mg/day for 5 to 7 days- 0 days
- systemic or oral prednisolone > 10 days and dose <10 mg/d 0 days
- systemic or oral prednisolone > 10 days and Dose >10 mg/day 28 days
- Antidepressants- 15 days
- Tranquilizers – 7day