How Long Do Allergy Shots Last? Treatment Length vs. Benefit Duration

Most patients notice initial symptom improvement within 3-6 months of starting allergy shots, often coinciding with the transition from the build-up phase to maintenance. The AAAAI/ACAAI Practice Parameter states that clinical improvement is usually observed within one year of reaching the maintenance dose. Early improvement reflects the initial desensitization of mast cells and basophils and rising IgG4 blocking antibody levels. However, the most significant and durable results typically emerge in years 2-3 of treatment as immune remodeling deepens. If no meaningful improvement is observed after one full year at the maintenance dose, your allergist should reassess allergen selection, dosing adequacy, and environmental exposure levels.

Stopping after 3 years is generally acceptable if the minimum maintenance threshold has been met and you have experienced meaningful symptom improvement. The EAACI 2018 guidelines specify 3 years as the minimum for achieving the disease-modifying effect that persists post-treatment. Some patients stop at 3 years without relapse; others benefit from extending to 5 years, which appears to produce longer post-treatment benefit in observational data. Marogna et al.'s 15-year SLIT study found no additional benefit beyond 5 years of treatment duration. The decision to stop should be made with your allergist based on your symptom response, allergen type, and individual risk of relapse — and if the weekly clinic trip is what makes finishing 3-5 years hard, an at-home option such as Curex lets you self-administer the same shots on the same schedule so you can reach the threshold that unlocks lasting benefit. Some patients require retreatment after 7-10 years if symptoms recur.

Stopping allergy shots before completing 3 years of maintenance is associated with significantly higher relapse rates. The GRASS trial (Scadding et al., JAMA 2017) provides direct evidence: neither 2 years of SCIT nor 2 years of SLIT was significantly better than placebo one year after stopping — demonstrating that 2-year courses are insufficient for durable benefit. Early discontinuation means the immune remodeling is incomplete, and the tolerance that has been built degrades more rapidly without the full consolidation that comes from 3+ years of consistent maintenance dosing. The cost-benefit calculation of immunotherapy — the long post-treatment benefit period — is only unlocked by completing the minimum recommended course.

Allergy shot benefits do not last forever, but they can persist for many years after stopping treatment. The current best evidence, synthesized by Penagos and Durham in JACI (2022), estimates 7-12 years of post-treatment benefit following a complete 3-5 year course. The longest individual follow-up — Eng et al. (2006) with 12 years of follow-up in 22 patients — found that clinical benefit was sustained even though skin-test reactivity had returned to baseline, suggesting the immune system's clinical tolerance outlasts the measurable sensitization changes. Eventually, some patients experience gradual symptom return and may benefit from a second course of immunotherapy, which typically works more rapidly than the first course.

Yes, evidence suggests that longer treatment courses (4-5 years vs 3 years) tend to produce more durable post-treatment benefit. Marogna et al.'s 15-year mite SLIT observational study found post-treatment benefit lasting approximately 7 years after a 3-year course and 8 years after 4- or 5-year courses, with no additional benefit beyond 5 years. For SCIT specifically, the 2011 AAAAI/ACAAI Practice Parameter recommends 3-5 years, with 5-year courses potentially offering longer remission in patients willing to continue. The incremental benefit of extending from 3 to 5 years likely depends on the allergen type, individual immunological response, and baseline sensitization severity — making this an individualized decision best made with your treating allergist.

Currently, no validated biomarker reliably predicts individual durability of response after stopping allergy shots. Allergen-specific IgG4 levels rise during treatment and correlate with efficacy, but Eng et al.'s 12-year follow-up showed that skin-test reactivity and presumably IgG4 returned toward baseline while clinical benefit persisted — meaning peripheral sensitization markers are imperfect surrogates for durable immune tolerance. Predictors of longer-lasting remission identified in observational studies include monosensitization (single allergen vs. multiple), younger age at treatment initiation, shorter disease duration before starting, and higher baseline specific IgE. The absence of a reliable predictive biomarker means that treatment decisions about duration and retreatment must rely on clinical symptom assessment rather than laboratory testing.