I stopped allergy shots — did I waste that time? What now?

It depends on how far you got. Immunotherapy produces progressive immune changes, and the amount retained correlates with treatment duration.

Quit during buildup (first 4-6 months): Minimal retained benefit. Buildup doses are sub-therapeutic — they're escalating toward the effective maintenance dose. The immune system has begun recognizing the allergen but hasn't yet shifted significantly toward tolerance. Starting drops now is essentially starting fresh.

Completed buildup, quit during early maintenance (6-18 months): Some retained benefit. Your immune system reached therapeutic allergen exposure levels and began producing IgG4 blocking antibodies and regulatory T cells. A JACI study confirmed that 2 years of immunotherapy produced measurable efficacy but was "insufficient to induce long-term tolerance" (Penagos & Durham, PMID: 35818157). You have partial immune priming that may give SLIT a slight head start.

Completed 2+ years of maintenance, quit before year 3: Moderate retained benefit. You likely have meaningful immune remodeling — but the critical threshold for sustained, long-term tolerance is 3 years of continuous treatment. Stopping at year 2 means higher relapse risk than completing year 3.

Completed 3+ years then stopped: You may have achieved the full disease-modifying effect. 70-80% of 3+ year completers maintain sustained improvement for 7-10+ years. If your symptoms returned years later, it may warrant a shorter SLIT "booster" course rather than a full restart.

The only published guideline for mid-course SCIT-to-SLIT switching comes from the Brazilian Association of Allergy and Immunology (ASBAI 2024, PMID: 38975257). No AAAAI, ACAAI, EAACI, or WAO guideline addresses this specific scenario.

Key ASBAI recommendations:
- Use allergen extracts from the same supplier when possible
- If the SCIT patient completed induction, switch to SLIT maintenance doses from the beginning — no re-escalation needed
- No formal washout period is required between stopping shots and starting drops
- Clinical evaluation monthly initially during the transition
- The immunomodulation from SCIT and SLIT may be complementary — prior shot exposure doesn't conflict with sublingual delivery

The largest dataset on route switching (4,933 children over 18 years, cited in ASBAI 2024 guideline, PMID: 38975257) found that 8.3% of SCIT patients switched to SLIT, primarily due to side effects. Safety was confirmed: no increase in adverse events from the switch.

Save your money if:

You quit shots because immunotherapy wasn't working, not because of logistics. If you completed 12+ months of maintenance SCIT and saw zero symptom improvement, the issue may be allergen selection, extract quality, or a non-allergic component to your rhinitis — not just the delivery route. Switching to drops with the same allergens at different concentrations may not solve the underlying problem. Reassess with allergy testing.

Your symptoms are now mild and manageable with OTC. If your allergy burden decreased since stopping shots — whether from natural tolerance, reduced exposure, or partial treatment benefit — a new 3-5 year drops commitment may not be proportionate. See if $15-30/month of OTC medication is sufficient before adding $39-99/month of SLIT.

You know you won't take daily drops for 3 years. 87-90% of SLIT patients quit before 3 years — even worse than the 75% shot dropout rate. If weekly clinic visits weren't sustainable, honestly assess whether unsupervised daily drops will be different. Without external accountability, adherence typically drops, not rises.

You're considering drops purely because they're cheaper. Drops cost $39-99/month ($470-1,200/year). If your insurer covered shots with $0-5 copay, your shot cost may have been lower. And shots have better completion rates. The convenience advantage is real; the cost advantage depends on your insurance.