Should allergy immunotherapy build‑up injections be administered intradermally or subcutaneously in the upper arm (deltoid)?

Allergy Build-Up Injections Should Be Administered Subcutaneously in the Upper Arm

Allergy immunotherapy build-up injections must be given subcutaneously—not intradermally—in the posterior portion of the middle third of the upper arm at the junction of the deltoid and triceps muscles. 1

Route of Administration: Subcutaneous Only

The standard of care is unequivocal: subcutaneous injection is the correct route for allergen immunotherapy. 1 Intradermal administration is explicitly contraindicated for routine allergy immunotherapy because:

• Subcutaneous injection creates a reservoir that allows slow, controlled absorption of allergen extract
• Intradermal injection risks too-rapid absorption, similar to intramuscular injection, which can precipitate systemic reactions and anaphylaxis 1
• The skin should be pinched and lifted off the muscles to ensure subcutaneous—not intramuscular or intradermal—delivery 1

While research studies have explored intradermal allergen administration for experimental purposes 2, 3, these are investigational approaches, not standard clinical practice. The established guidelines are clear that subcutaneous is the only appropriate route for routine allergen immunotherapy. 1

Specific Injection Site

The injection must be given in the posterior portion of the middle third of the arm at the junction of the deltoid and triceps muscles. 1 This location is chosen because:

• It has a greater amount of subcutaneous tissue than adjacent areas
• This reduces the risk of inadvertent intramuscular injection
• The location provides optimal subcutaneous access when proper technique is used

Technical Requirements

Needle Specifications

Use a 26- to 27-gauge syringe with a ½- or ⅜-inch nonremovable needle specifically designed for immunotherapy. 1

Critical Technique Points

1. Pinch the skin to lift it off underlying muscle, ensuring subcutaneous access 1
2. Wipe the area with an alcohol swab before injection 1
3. Depress the plunger at a rate that does not result in wheal formation or excessive pain 1
4. Apply mild pressure for about 1 minute after needle removal to reduce allergen leakage 1

Important Safety Caveat

Be aware that 80% of patients have skin-to-muscle depth ≤13 mm, putting them at risk for inadvertent intramuscular injection with standard allergy syringes. 4 Intramuscular administration increases anaphylaxis risk due to rapid absorption. The proper technique of pinching and lifting the skin is therefore essential to maintain subcutaneous delivery and avoid this complication.