What is a sign that indicates successful administration of an intradermal injection?

A wheal at the injection site indicates successful administration of an intradermal injection because this localized raised area forms when the substance injected is deposited within the dermal layer of the skin. Intradermal injections are specifically designed to introduce a small volume of fluid just beneath the skin's surface, and the formation of a wheal is the expected response. This reaction occurs as the body responds to the injected material, leading to localized edema and a specific immune response.

Other potential responses such as bruising, no visible reaction, or pain may arise in various scenarios but are not definitive indicators of a successful intradermal injection. Bruising may occur due to damage to blood vessels in the area, indicating a problem rather than success. A lack of visible reaction does not confirm the effectiveness of the injection, as no wheal means the injection may not have been properly administered. Pain at the site can happen with various types of injections, but it does not provide a reliable sign of successful intradermal administration. Thus, the presence of a wheal serves as the key indicator of a successful intradermal injection.