Allergy Shots Timeline: Build-Up, Maintenance, and Remission Phases

The allergy shots timeline has three named phases per Cox 2011 PP3. Phase 1 — Build-up (Months 0–6): approximately 24–28 weekly injections escalating from the most dilute vial to the maintenance concentrate. The hardest phase: 23.9% of AIT patients never return after the first injection (Tkacz 2021). Phase 2 — Early maintenance (Months 6–12): every-2-week visits with the dose stable at the maintenance concentrate; subjective symptom improvement typically begins here. Phase 3 — Full maintenance (Years 2–5): every 2–4 weeks (most clinics monthly); the disease-modifying tolerance per Durham 1999 NEJM accumulates; full symptom benefit achieved by Year 2–3. Post-treatment: 7–10 years of durable remission per Jacobsen 2007 PAT.

Most patients begin to notice subjective improvement during Phase 2 — early maintenance, approximately 6–12 months into the allergy shots timeline. The typical first signs are reduced nasal symptoms during the first peak allergen season after reaching maintenance, less frequent rescue antihistamine use, and improved sleep quality. Full benefit typically solidifies by Year 2–3 of full maintenance. The immunological changes begin earlier — IgG4 blocking antibodies rise within months of build-up — but the clinical threshold most patients notice takes longer. Per the Calderon 2007 Cochrane review (51 RCTs, n=2,871), the pooled symptom SMD is −0.73, corresponding to roughly a one-third reduction in symptom severity.

The build-up phase is where the immune tolerance induction process is initiated. Each weekly injection gradually escalates the allergen dose, allowing regulatory T cells to expand and IgG4 blocking antibodies to begin rising before the patient is exposed to the full maintenance dose. Without completing build-up — or without completing it slowly enough to avoid systemic reactions — the patient never reaches the therapeutic dose required for disease-modifying benefit. Build-up is also where most dropout occurs: Tkacz 2021 found 23.9% of AIT patients never returned after their first injection. Patients who persist through the 6-month build-up have substantially higher odds of completing the full treatment course.

Yes — durable post-treatment benefit is one of the defining advantages of allergen immunotherapy. Durham et al. (NEJM 1999) showed that 3–4 years of grass-pollen SCIT produced "a persistent alteration in immunologic reactivity" lasting years after stopping. Jacobsen et al. (Allergy 2007) 10-year PAT follow-up found that a 3-year SCIT course in allergic children reduced new asthma onset for up to 7 years post-treatment (adjusted OR 4.6). Möller et al. (JACI 2002) confirmed the 3-year PAT benefit. This post-treatment durability is the primary reason to complete the full maintenance phase rather than stopping early: stopping at Year 1 or 2 substantially reduces the likelihood of achieving this sustained benefit.

The allergy shots timeline requires a 3-to-5-year clinic-visit commitment but produces benefit that persists 7–10 years after stopping per Durham 1999 and Jacobsen 2007 PAT. Daily antihistamines require ongoing daily use for ongoing benefit — there is no post-treatment durability. The Cochrane meta-analysis (Calderon 2007) confirmed that SCIT produces SMD −0.73 for symptom scores and SMD −0.57 for medication use — meaning most patients need significantly less pharmacotherapy during and after treatment. The 5-year SCIT investment therefore pays dividends across a 12+ year window, whereas antihistamine cost and use accumulates indefinitely. For patients who can complete the full timeline, the lifetime cost-benefit calculation often favors SCIT over permanent pharmacotherapy.