Allergy screening (allergy tests, skin prick tests)

Skin tests are a fundamental method for diagnosing allergies, helping to identify substances that trigger allergic reactions.

They are primarily used for food allergies, allergic rhinitis, asthma, drug allergies, and insect sting allergies.

Types of Skin Tests

1. Skin Prick Test

It is the most commonly used method for diagnosing aeroallergens (e.g., pollen, dust mites, molds/fungi, animal dander) and food allergies.

How it's done:

1. Drops containing allergens are applied to the surface of the skin (usually on the forearm or back).
2. A small prick is made on the skin's surface with a fine needle (lancet) to allow the allergen to enter.
3. After 15-20 minutes, the reaction (redness or wheals) is evaluated.

• Results
  • If swelling (≥3mm diameter) appears, the test is considered positive.

• Advantages
  • Quick (results in 15-20 minutes)
  • Minimally invasive
  • High sensitivity

• Limitations
  • Not applicable to individuals taking antihistamines (they must be discontinued 5-7 days prior).
  • Not suitable for individuals with severe allergies due to the risk of anaphylaxis.

2. Intradermal Test

• A small amount of allergen is injected intradermally with a fine needle.
• The reaction is evaluated after 15-20 minutes

• Advantages
  • Higher sensitivity than the Prick Test

• Limitations:
  • Higher risk of anaphylaxis
  • Not used for food allergies

3. Patch Test

• It is used for the diagnosis of allergic contact reactions, e.g., contact dermatitis from metals (nickel), cosmetics, medications, or chemicals.

• How it's done:
  • Adhesive patches containing allergens are placed on the back.
  • The test is checked after 48 hours and re-evaluated at 72-96 hours.

• Advantages
  • Useful for contact allergies not detected by Prick/Intradermal Tests.

• Limitations
  • Slow results (takes days).
  • Doesn't detect immediate allergic reactions.

Indications for Skin Tests

• Allergic rhinitis & conjunctivitis (pollen, dust mites, molds/fungi).
• Asthma with allergic etiology.
• Food allergies (milk, egg, nuts, fish, soy).
• Drug allergies (e.g., antibiotics, local anesthetics).
• Insect sting allergies (bee, wasp).
• Contact dermatitis (cosmetics, metals, chemicals).

Contraindications & Precautions

• Severe or uncontrolled asthma.
• History of anaphylaxis (requires caution).
• Taking antihistamines or corticosteroids.
• Skin conditions affecting the test area (e.g., eczema).