Final answer:
TRUE. A wheal forming at the site of a skin test indicates an allergic reaction to the serum.
Step-by-step explanation:
A wheal forming at the site of a skin test indicates an allergic reaction to the serum. The statement is TRUE.
Allergists use skin testing to identify allergens in type I hypersensitivity. In skin testing, allergen extracts are injected into the epidermis, and a positive result of a soft, pale swelling at the site surrounded by a red zone (called the wheal and flare response), caused by the release of histamine and the granule mediators, usually occurs within 30 minutes.
The formation of a wheal at the site of a skin test is a characteristic response to an allergic reaction, indicating that the immune system has recognized the allergen and produced an immune response.