The intradermal (ID) route involves administering medication into the dermis layer of the skin, located just beneath the epidermis. Because this layer has a rich vascular supply and numerous nerve endings, absorption of the medication occurs very slowly compared to subcutaneous or intramuscular routes. This slow absorption rate makes the intradermal route ideal for diagnostic testing, where systemic effects are undesirable and localized tissue reactions need to be closely observed. Nurses must understand that the dermis is very thin, requiring precise needle placement to prevent accidental subcutaneous injection.
Nurses utilize the intradermal route primarily for diagnostic evaluations rather than therapeutic treatment. Common indications include:
Administering medication intradermally demands specialized equipment to ensure accuracy. Because the dose is exceptionally small—usually between 0.01 mL and 0.1 mL—standard syringes are unsuitable.
Choosing the correct anatomical site ensures reliable assessment and easy observation of skin reactions. The inner aspect of the forearm is the preferred site because it is relatively hairless, lacks major blood vessels, and allows clear visibility of any localized reaction. The upper back is another acceptable site, often used when multiple allergy panels are evaluated simultaneously. Nurses must avoid areas with lesions, tattoos, excessive hair, or prominent veins.
Proper technique ensures the medication forms a visible bleb under the epidermis.
Evaluating skin tests requires strict adherence to timing and measurement guidelines. For a tuberculin skin test, the nurse must inspect the site 48 to 72 hours after administration. Assessment focuses on palpating and measuring the diameter of induration—the hard, raised, palpable area—rather than measuring any surrounding redness or erythema. Documenting the exact size in millimeters and noting the presence of necrosis or blistering is essential for accurate clinical diagnosis.
Although generally safe, intradermal injections carry minor risks that nurses must manage. Localized pain, stinging during injection, and mild pruritus at the site are common and expected. If medication leaks onto the surface because the needle was inserted too shallowly, or if no bleb forms, the test must be repeated at a different site. Severe allergic reactions or anaphylaxis are rare during diagnostic tests, but emergency equipment must remain readily accessible whenever foreign proteins or allergens are administered.