Shot for Allergy: Why One Shot Is Never the Answer

No single injection cures allergies. The closest evidence-based answer is subcutaneous immunotherapy (SCIT), a multi-year course of weekly then monthly injections that produces durable post-treatment remission. Durham SR et al (NEJM 1999) found that a 3-year grass-pollen SCIT course maintained benefits comparable to ongoing treatment for at least 4 years after stopping — but this required completing the full multi-year course, not a single injection. Depot corticosteroid injections (Kenalog, Depo-Medrol) provide brief symptom suppression in one visit but are not disease-modifying and are professionally discouraged for routine use by the AAAAI/ACAAI rhinitis practice parameter.

A steroid allergy shot (Kenalog-40 or Depo-Medrol) is an intramuscular depot corticosteroid that broadly suppresses the immune system, providing symptom relief for days to three weeks. It is a symptomatic intervention only — it does not modify the underlying allergy and has no lasting benefit once the drug clears. Allergy immunotherapy (SCIT) is a multi-year course of subcutaneous allergen extract injections that retrains the immune system to tolerate specific allergens through regulatory T-cell induction and blocking IgG4 antibodies. SCIT is the only injection-based allergy intervention with documented durable post-treatment remission in randomized trials.

In Year 1, SCIT involves approximately 39 in-person clinic visits — roughly 26-28 weekly build-up injections followed by approximately 13 early-maintenance visits at 2-4 week intervals per the Cox 2011 Practice Parameter Third Update. In Years 2 through 5 (the maintenance phase), patients receive 14-26 injections per year depending on their dosing interval. Over a complete 3-year course, most patients receive approximately 57-60 injections total. Each visit requires a mandatory 30-minute post-injection observation period, making each appointment approximately 45 minutes total.

Most patients notice meaningful symptom improvement within 3-6 months of reaching the maintenance dose — typically after completing the 6-month build-up phase and the first few months of maintenance. Some patients notice partial improvement during build-up as early immune changes begin. However, full disease-modifying benefit accumulates over the entire 3-5 year course. Clinical evidence shows that 2-year courses are insufficient for durable post-treatment remission (Scadding et al, JAMA 2017), while 3-year courses produce lasting results documented by Durham et al (NEJM 1999). Judging effectiveness at 2-3 months of build-up is premature.

Stopping SCIT after only a few visits typically means no lasting benefit — the immune changes that produce durable remission require completing the full 3-5 year course. There are no serious safety risks from discontinuing early, but the time and cost invested to that point will not have produced the disease-modifying outcome. If a patient cannot tolerate injections due to persistent large local reactions or systemic reactions during build-up, their allergist can adjust the protocol, consider a slower schedule, or discuss sublingual immunotherapy as an alternative. Any decision to stop should be made with the treating allergist, not unilaterally.

SCIT (subcutaneous immunotherapy) costs vary substantially by insurance status. With commercial insurance, most patients pay $15-50 per visit in copays — roughly $600-2,000 in copays for Year 1's 39 visits alone, before deductibles and extract preparation fees. Without insurance, annual SCIT costs range from approximately $1,000-4,000 depending on region. The CMS 2025 Physician Fee Schedule sets Medicare allowed amounts at $11.97 for CPT 95117 (two or more injections per visit) and $13.91 per dose for CPT 95165 (extract preparation). Indirect costs — approximately 110 hours of clinic time over 3 years plus travel — represent a substantial additional commitment.