intradermaal

Intradermaal, commonly spelled intradermal, refers to a route of administration in which a small amount of substance is injected into the dermis, the skin layer just beneath the epidermis. This is distinct from subcutaneous and intramuscular injections, which place material deeper in the skin or into muscle tissue. The intradermal space contains many antigen-presenting cells, which can influence immune responses to certain substances.

Technique and administration are defined by depth and volume. A fine needle (typically 25–27 gauge) is inserted shallowly, at a small angle, to deposit material into the dermis rather than the subcutaneous tissue. The resulting localized reaction, often a small raised wheal, is used to gauge response or absorption depending on the purpose. Typical test volumes are small, around 0.1 mL for skin tests, and the site is observed for defined reactions rather than systemic effects.

Common uses include testing for tuberculosis exposure, via the Mantoux tuberculin skin test, which employs intradermal tuberculin to elicit an induration that is measured after 48–72 hours. Intradermal injections are also used in allergy testing, where small amounts of allergens are introduced into the dermis. In certain vaccines, intradermal administration has been explored or employed to reduce antigen dose and stimulate a robust local immune response, though most vaccines are given by other routes.

Safety and accuracy depend on proper technique and site selection. Potential risks include local skin reactions and, rarely, infection. Contraindications include active skin disease at the injection site and certain bleeding disorders.