Management of Injection Site Reactions Post Allergy Shot
For injection site reactions after allergy shots, apply cold compresses to the area, administer oral antihistamines for symptomatic relief, and monitor for progression to systemic reactions. 1
Classification of Reactions
Reactions to allergen immunotherapy are typically classified into two categories:
Local reactions:
- Redness, swelling, pruritus (itching), and pain at the injection site
- Generally self-limiting and not predictive of systemic reactions
- Do not typically require modification of subsequent immunotherapy doses
Systemic reactions:
- Range from mild (Grade 1) to severe/life-threatening (Grade 4-5)
- Require immediate recognition and appropriate treatment
Management Algorithm for Injection Site Reactions
Immediate Management
Assessment of reaction severity:
- Determine if the reaction is limited to the injection site or involves systemic symptoms
- Measure the size of any local swelling (diameter in cm)
- Note presence of erythema, pruritus, or pain
For localized reactions only:
- Apply cold compresses to reduce swelling and discomfort 1
- Administer oral antihistamines for symptomatic relief
- Monitor the patient for at least 30 minutes to ensure the reaction remains localized
For large local reactions (>2.5 cm in diameter):
- Apply cold compresses
- Consider oral antihistamines
- Document the size and duration of the reaction
- Consider dose adjustment for subsequent immunotherapy
Follow-up Management
Documentation:
- Record the size, duration, and characteristics of the reaction
- Note any treatments administered and their effectiveness
Subsequent dose considerations:
- For significant local reactions, the allergist may consider adjusting the next dose
- Persistent large local reactions may warrant maintaining or reducing the dose rather than increasing it
Special Considerations
Persistent Subcutaneous Nodules
- May develop at injection sites, particularly with aluminum hydroxide-containing extracts 2
- Usually resolve spontaneously over weeks to months
- Warm compresses may help accelerate resolution
- Rarely require medical intervention
Risk Factors for Severe Reactions
- Poorly controlled asthma 1
- Previous systemic reactions to immunotherapy
- Concurrent use of β-adrenergic blocking agents 1
- High degree of sensitivity to allergen
Patient Education
Instruct patients to:
- Report significant local reactions
- Recognize early signs of systemic reactions
- Understand the difference between normal local reactions and concerning symptoms
Injection technique education:
- Proper subcutaneous (not intramuscular) administration
- Use of 26-27 gauge needles with half-inch length 1
- Injection into the posterior portion of the middle third of the upper arm
When to Seek Immediate Medical Attention
Patients should be instructed to seek immediate medical attention if they experience:
- Difficulty breathing or swallowing
- Dizziness or lightheadedness
- Generalized itching or hives away from the injection site
- Nausea, vomiting, or abdominal cramping
Common Pitfalls and Caveats
Do not confuse local reactions with systemic reactions:
- Local reactions are confined to the injection site
- Systemic reactions involve symptoms beyond the injection site
Do not ignore large local reactions:
- Document and consider for dose adjustment
- May indicate increased risk for future systemic reactions
Do not administer repeated injections at the same site:
- Can cause tissue necrosis due to vasoconstriction 3
- Rotate injection sites
Do not discharge patients too early:
By following these guidelines, most injection site reactions can be effectively managed while minimizing the risk of progression to more serious systemic reactions.