Which testing method involves injecting a small amount of antigen under the skin to observe a reaction?

Which testing method involves injecting a small amount of antigen under the skin to observe a reaction?

• A. Scratch test
• B. Prick test
• C. Intradermal allergy testing
• D. Skin patch test

Answer: (C)

Intradermal allergy testing involves injecting a small amount of antigen into the dermis, just under the skin. This puts the allergen directly into a layer with many immune cells, so the test is more sensitive and can reveal reactions that surface tests might miss. After injecting, the clinician watches for a wheal (a raised bump) and surrounding redness within about 15–20 minutes, which indicates a positive reaction. This method is used when a stronger test is needed or when other tests aren’t conclusive, such as for certain venom or drug allergies. The other common skin tests differ in how the antigen is introduced: scratch testing involves scratching the skin and applying antigen on the surface; prick testing places a tiny prick to allow antigen to enter near the surface; skin patch testing applies patches with allergens to the skin for 24–72 hours to assess delayed reactions.

Intradermal allergy testing involves injecting a small amount of antigen into the dermis, just under the skin. This puts the allergen directly into a layer with many immune cells, so the test is more sensitive and can reveal reactions that surface tests might miss. After injecting, the clinician watches for a wheal (a raised bump) and surrounding redness within about 15–20 minutes, which indicates a positive reaction.

This method is used when a stronger test is needed or when other tests aren’t conclusive, such as for certain venom or drug allergies. The other common skin tests differ in how the antigen is introduced: scratch testing involves scratching the skin and applying antigen on the surface; prick testing places a tiny prick to allow antigen to enter near the surface; skin patch testing applies patches with allergens to the skin for 24–72 hours to assess delayed reactions.