An intradermal injection delivers a small volume of substance into the dermis, the skin layer between the epidermis and hypodermis. This method is chosen for its slow absorption rate and localized effect, making it suitable for sensitivity tests and vaccinations that require a visible reaction.
Primary Intradermal Injection Sites
Selecting the appropriate injection site is vital for safety and accuracy. Sites should be free from any skin abnormalities that could affect the procedure or results.
Inner Forearm
The inner forearm is the most frequent location for intradermal injections, particularly for tuberculosis testing. It is typically located 2 to 4 inches below the elbow. This site is preferred because its thin skin allows for clear visualization of the injection and the resulting wheal, which is essential for accurate test readings.
Upper Back
The upper back, beneath the shoulder blade, is another viable site, often used for extensive allergy testing due to its large surface area. This site can be especially useful for children or when the forearm is not accessible.
Deltoid Area
In some instances, the deltoid region of the upper arm can be used as an alternative site for certain vaccines administered intradermally, such as the JYNNEOS vaccine.
Intradermal Injection Procedure Overview
Administering an intradermal injection requires a specific technique to ensure the substance reaches the dermis.
Step-by-Step Administration
- Prepare the site by cleaning it with an alcohol swab after performing hand hygiene and donning gloves.
- Hold the skin taut with your non-dominant hand.
- Insert the needle at a 5- to 15-degree angle with the bevel facing up, just until the bevel is covered.
- Inject the substance slowly, observing for the formation of a wheal.
- Withdraw the needle at the insertion angle and discard it in a sharps container. Avoid massaging the site.
Comparison of Injection Types
Here is a comparison highlighting the differences between intradermal, subcutaneous, and intramuscular injections:
| Feature | Intradermal (ID) | Subcutaneous (SC) | Intramuscular (IM) |
|---|---|---|---|
| Injection Layer | Dermis, just below the epidermis | Adipose (fatty) tissue beneath the dermis | Deep into the muscle |
| Injection Angle | 5 to 15 degrees | 45 or 90 degrees | 90 degrees |
| Absorption Time | Longest absorption time | Slower than IM or IV | Rapid absorption |
| Common Sites | Inner forearm, upper back, deltoid | Abdomen, upper arm, thigh | Deltoid, vastus lateralis, ventrogluteal |
| Dose Volume | Very small (usually <0.5 mL) | Small (up to 1 mL) | Larger (up to 3 mL for adults) |
| Common Uses | TB test, allergy testing | Insulin, certain vaccines | Vaccines, antibiotics |
Potential Complications and Patient Education
While generally safe, improper technique, such as injecting too deeply, can lead to inaccurate test results. Other potential complications include minor bleeding, pain, itching, or, less commonly, blistering or scarring.
Patients should be instructed not to massage the site to avoid spreading the substance and altering results. For tests like the TST, patients must return within 48 to 72 hours for reading. They should also be advised to report any signs of a severe reaction.
Conclusion
Knowing where can you give intradermal injections is essential for accurate diagnostic testing and effective therapy. The inner forearm and upper back are the preferred sites due to their suitability for this technique. Correct administration and patient education are key to successful outcomes and minimizing complications. The CDC provides further resources on safe injection practices.
