Administering Intradermal Injections

Core Concepts

The Target Layer: Skin Anatomy

The skin has three main layers. The epidermis is the thin, tough outer layer. Beneath it is the dermis, a layer of connective tissue containing small blood vessels, nerves, and glands. Beneath the dermis lies the subcutaneous layer of fat. An ID injection targets the dermis only — the needle barely penetrates. The dermis's limited blood supply is the whole point: slow absorption keeps the medication local so the body's reaction (redness, swelling, firmness) can be observed over hours to days.

Choosing the Site

The best sites are hairless, lightly pigmented, and free of irritation, so that a subtle reaction can be seen clearly. The inner forearm is the most common site; the upper chest and the upper back (below the scapula) are alternatives. The nurse avoids areas with veins, scars, tattoos, rashes, or broken skin — a reaction can be hidden or mimicked there. For repeated testing, sites are marked and rotated per policy.

Supplies

ID injections use a small-gauge, short needle (commonly around 25–27 gauge and roughly 3/8–1/2 inch — educational ranges; the specific product and policy govern), mounted on a tuberculin syringe (1 mL with fine graduations) so tiny volumes can be measured accurately. The small volume — often about 0.1 mL for many skin tests — is specified by the test's instructions; the nurse measures exactly and never "eyeballs" a dose this small.

Technique, Step by Step

1. Verify the order, rights, and allergies; gather supplies; perform hand hygiene.
2. Select and inspect the site; clean it with an antiseptic swab and let it dry — wet antiseptic stings and can alter the injection.
3. Stretch the skin taut with the non-dominant hand so the needle can glide into the dermis cleanly.
4. Insert the needle at a 5–15 degree angle, bevel up, until the bevel is just visible through the skin — if you can see the bevel, you are in the dermis, not deeper.
5. Inject slowly. A wheal should form — a small, pale, raised bleb. If no wheal appears, the injection was likely too deep; per policy, the test may need to be repeated at another site.
6. Withdraw the needle and activate the safety device; dispose of the sharps immediately.
7. Do not massage or rub the site. Per policy, the site may be circled or marked so the reader can find it later; document the site, time, and solution.

Observing for Adverse Reactions

Because ID tests are themselves tiny exposures to substances (allergens or test antigens), the nurse watches for more than the local site. A severe allergic response — difficulty breathing, hives spreading beyond the site, facial swelling, dizziness — is an emergency regardless of the test's purpose, and the nurse must know the facility's emergency response plan and how to summon help. Most reactions are mild and local (itching, redness), but the possibility of a serious response is exactly why skin testing is done in a setting where observation and response capability exist. The nurse also checks the site before the patient leaves, confirms the patient knows what to report, and documents any reaction observed during the placement visit itself.

Reading, Teaching, and Documentation

The reaction is read at the time specified by the test and the order (for many TB screening tests, that is 48–72 hours after placement — educational example; the specific test's instructions govern). What is measured matters: a positive reaction is judged on induration — a firm, raised area — not simply on redness (erythema), which can be a normal irritant response. Reading is done by qualified personnel per policy. Patient teaching starts immediately: don't scratch the site, don't cover it with a bandage that could rub it, keep it clean, and report any unusual pain, spreading redness, or discomfort. The nurse documents placement and, when applicable, the reading result and what the patient was told.

Common Confusions