What action should a medical assistant take when administering an intradermal injection for allergy testing?

When administering an intradermal injection for allergy testing, locating the middle portion of the anterior forearm is the correct approach. This area is chosen because the skin on the forearm is typically thinner and more sensitive, which allows for a clear view of the response to the allergen being tested. The intradermal injection technique involves injecting a small amount of the allergen just beneath the skin, and the forearm is the ideal site for monitoring any immediate reactions.

Other areas mentioned in the choices may not be suitable for intradermal injections. For instance, injecting into the upper thigh or the deltoid area can lead to deeper injections than intended, which could hinder the ability to read the allergic reaction accurately. Additionally, it is unnecessary to apply a tourniquet before an intradermal injection, as this could cause discomfort and may not provide any benefit for this type of procedure. Thus, the anterior forearm remains the most appropriate and effective site for such tests.