Which method is primarily used to assess drug sensitivity?

The primary method used to assess drug sensitivity is intradermal injection. This technique involves administering a small amount of a substance just beneath the surface of the skin, allowing for localized reactions that can indicate an individual's sensitivity to that drug or allergen. The spleen and lymph nodes are involved in the immune response, and by observing the reaction at the injection site—such as redness, swelling, or other signs of a hypersensitive reaction—healthcare providers can evaluate how the patient's immune system responds to the drug.

Intradermal injections are particularly useful for testing allergies and evaluating reactions to medications, which is why this method is chosen for assessing drug sensitivity rather than the other options. Other methods such as subcutaneous or intramuscular injections deliver the substance deeper into the body, where it may not provide immediate and clear indications of sensitivity. Topical application involves applying medication to the skin surface primarily for localized treatment rather than assessment, which also makes it less suitable for evaluating drug sensitivity compared to intradermal injection.