Allergy Shots (Subcutaneous Immunotherapy)
Allergy shots are indicated for patients with allergic rhinitis (with or without asthma) who have documented IgE-mediated sensitivity to clinically relevant allergens confirmed by testing, when symptoms are inadequately controlled by allergen avoidance and pharmacotherapy. 1
Absolute Contraindications
Do not initiate SCIT in patients who:
Relative Contraindications (Use Caution)
Consider avoiding SCIT in patients with:
Dosing Schedule
Build-Up Phase
Starting dose: Begin at 1:10,000 or 1:1,000 dilution of maintenance concentrate; use more dilute concentrations (lower starting doses) for highly sensitive patients based on history and skin test reactivity 2.
Frequency: Administer 1-3 injections per week during conventional build-up 2. The interval between injections can be as short as 1 day without increased systemic reactions if clinically necessary 2.
Timeline: Expect to reach maintenance dose in 3-6 months with conventional schedules 2.
Accelerated options: Cluster immunotherapy (2+ injections per visit at 30-minute intervals) can achieve maintenance in as little as 4 weeks 2.
Maintenance Phase
Frequency: Every 3-4 weeks once maintenance dose is achieved 3.
Duration: Treat for minimum 3 years; continue based on patient response 1.
Dose Adjustments for Missed Appointments
During Build-Up
Start reducing dose if patient presents 14 days after last scheduled injection; completely restart if gap exceeds 85-90 days 3.
During Maintenance
Start reducing dose if patient presents 5 weeks after last injection; completely restart if gap exceeds 12-16 weeks 3.
Critical caveat: These are consensus-based recommendations from practitioner surveys, not evidence-based protocols. No prospective studies exist to guide optimal dose adjustment 2, 3.
Managing Systemic Reactions
If systemic reaction occurs: Reduce the dose to a previously tolerated level or lower if reaction was severe 2. Do not simply continue at the same dose.
Seasonal considerations: While some experts suggest dose reduction during peak allergen seasons for highly sensitive patients, two large prospective studies (totaling >850,000 injections) found no increased systemic reactions during pollen seasons 2. Most patients tolerate continued dose escalation without seasonal adjustment.
Critical Safety Requirements
Mandatory safety measures:
- Administer injections only in settings with immediate access to epinephrine and equipment to treat anaphylaxis 2
- Observe patients for 30 minutes post-injection 2
- Epinephrine should be administered intramuscularly in the thigh for optimal pharmacokinetics 2
- Screen for uncontrolled asthma before every injection 1
Major risk factors for systemic reactions:
- Highest allergen extract concentration (all systemic reactions in one quality improvement study occurred at peak concentration) 4
- Uncontrolled asthma 4
- Seasonal exacerbation of allergic rhinitis 4
- Administration errors 4
Allergen Selection
Limit treatment to clinically relevant allergens that correlate with patient history and are confirmed by testing 1. Polysensitized patients can be treated with a limited number of allergens rather than all positive skin tests 1.
Common pitfall: Avoid treating every positive skin test. Select only allergens with clear clinical correlation to symptoms.
Patient Education Points
Educate patients that SCIT can:
- Prevent new allergen sensitizations 1
- Reduce risk of developing allergic asthma 1
- Provide continued benefit after discontinuation (disease-modifying effect) 1, 5
SCIT vs SLIT comparison: SCIT requires office visits with post-injection observation but has more established efficacy data for multiple allergens. SLIT offers home administration convenience but has a more limited evidence base for certain allergens 1.
Monitoring During Treatment
Do not repeat allergy testing to assess efficacy unless there is a change in environmental exposures or loss of symptom control 1. Testing does not predict treatment response.
Continue escalation with local reactions: Local reactions at injection site are not contraindications to dose advancement 1.