Allergy test

Overview

1. The Allergy Test is a specialized diagnostic examination designed to measure the body’s immune response to specific allergens. When the immune system mistakenly identifies a harmless substance (allergen) as a threat, it produces immunoglobulin E (IgE) antibodies that trigger the release of chemicals responsible for allergic reactions. These reactions can occur within minutes to a few hours after exposure to allergens.
2. Allergy tests are essential for identifying the specific allergen responsible for triggering allergic symptoms. They can detect airborne allergens (like pollen, dust, and pet dander), food allergens, insect venom, or chemical allergens that cause skin or respiratory issues.
3. This test measures either the total IgE (overall allergic tendency) or specific IgE antibodies that target individual allergens. By assessing IgE levels in serum or plasma, clinicians can determine the presence, type, and severity of allergic reactions.
4. Common methods include Turbidometry, Electrochemiluminescence Immunoassay (ECLIA), ELISA, Chemiluminescence, and Immunoblot. These techniques quantify allergen-specific antibodies to confirm hypersensitivity.

Symptoms

Allergy test results are used to confirm and understand the symptoms caused by allergen exposure. The reactions can affect the respiratory system, skin, gastrointestinal tract, and cardiovascular system.

1. Respiratory Symptoms (Airborne Allergens):
   1. Sneezing, nasal congestion, or runny nose.
   2. Shortness of breath, wheezing, or chronic cough.
   3. Itchy, watery eyes and sore throat.
   4. Headaches due to sinus inflammation.
   5. Commonly seen in allergic rhinitis (hay fever).
2. Food Allergy Symptoms:
   1. Occur within 30 minutes to 2 hours after eating specific foods.
   2. Skin manifestations like hives, itching, swelling of the face, lips, or tongue.
   3. Respiratory issues such as coughing, wheezing, chest tightness, or throat constriction.
   4. Gastrointestinal distress including abdominal pain, nausea, vomiting, and diarrhea.
   5. Severe reactions may cause pale skin, weak pulse, dizziness, or fainting.
3. Extrinsic Asthma and Atopic Eczema:
   1. Immediate reaction after allergen exposure.
   2. Mediated by IgE antibodies leading to inflammation and airway constriction.

Causes

The cause of allergy lies in the immune system’s overreaction to harmless environmental or dietary substances. The test helps identify which specific allergens provoke the immune response.

1. Airborne Allergens: Dust, pollen (birch, oak, willow, alder), animal dander (cat, dog, horse), and grass pollen (Bermuda grass, ragweed).
2. Food Allergens: Milk, wheat, soy, peanut, rice, potato, onion, tomato, apple, coconut, egg, and fish.
3. Fruits: Banana, pear, papaya, peach, kiwi, mango, pineapple.
4. Animal Allergens: Dander from cats, dogs, cows, and guinea pigs.
5. Non-Vegetarian Allergens: Chicken, beef, pork, cod fish, tuna, shrimp, and salmon.
6. The immune system reacts by producing allergen-specific IgE antibodies, which bind to mast cells and basophils, releasing histamine and other mediators that cause allergy symptoms.
7. Increased IgE levels (0–200 IU/mL normal range) indicate heightened allergic activity.

Risk Factors

Certain individuals are more susceptible to allergic reactions and may require regular testing:

1. Genetic Predisposition: Family history of allergies, asthma, or eczema increases risk.
2. Environmental Exposure: High exposure to dust mites, pollens, and pet dander.
3. Dietary Factors: Regular consumption of allergenic foods like peanuts, milk, or shellfish.
4. Occupational Hazards: Workers exposed to animal dander, molds, or chemicals.
5. Atopic Conditions: Individuals with asthma, hay fever, or chronic dermatitis.
6. Age and Lifestyle: Children and young adults are more prone to allergic sensitization.
7. Medication Influence: Certain medications can alter IgE levels or interfere with test accuracy.
8. Sample Handling Issues: Gross hemolysis, lipemia, or icterus can affect test results.

Prevention

While allergies cannot always be prevented, early detection and allergen avoidance can effectively manage and reduce the severity of reactions.

1. Specimen Collection and Handling:
   1. Use blood (serum or plasma) as specimen, with a minimum volume of 3 mL.
   2. Avoid gross hemolysis or lipemic samples; refrigerate samples at 2–8°C for up to 14 days.
2. Testing Techniques:
   1. Methods such as Chemiluminescence, Fluorescence, ELISA, and Immunoblot are used.
   2. Allergen Binding Principle: The allergen binds with specific IgE; enzyme-labeled antibodies form a measurable complex.
   3. Measurement: Fluorescence intensity correlates with allergen-specific IgE concentration.
3. Interpretation of Results:
   1. <0.35 kU/L: Undetectable; 0.35–1.5 kU/L: Low; 1.5–50 kU/L: High; 50–100 kU/L: Very High.
   2. Results ≥0.35 kU/L indicate allergen-specific IgE presence.
4. Assay Types:
   1. Singleplex Assay: Tests one allergen at a time, highly sensitive.
   2. Multiplex Assay: Detects multiple allergens simultaneously but may have interference from IgG antibodies.
5. Allergen Management:
   1. Identify and avoid specific allergens detected in testing.
   2. Maintain clean indoor environments to reduce dust and dander.
   3. Use air purifiers, hypoallergenic bedding, and humidity control to minimize triggers.
   4. For food allergies, strict avoidance and label checking are crucial.
   5. Seek medical consultation for immunotherapy or antihistamines if allergies persist.