An intradermal injection is given into which layer of skin?

• A. Subcutaneous Tissue
• B. Epidermis
• C. Muscle
• D. Dermis

Answer: (D)

Intradermal injections are placed into the dermis, the thin layer just beneath the outer epidermis and above the subcutaneous tissue. This location is ideal for testing the immune response because the dermis contains immune-presenting cells and a rich network of small vessels, so even a tiny amount of antigen can produce a localized wheal and a measurable reaction. If the injection went into the epidermis, it would be too superficial for the intended response. If it went into subcutaneous tissue, it would be a subcutaneous injection with different absorption and a different test outcome. If it reached muscle, it would be an intramuscular injection with another absorption profile.