When to Get Allergy Shots: Optimal Timing by Allergen Type and Season

The best time of year to start allergy shots depends on your specific allergen triggers. For spring tree and grass pollen allergies, starting in October through December gives you 3-4 months to complete build-up before the spring pollen season begins — typically March-May depending on your region. For fall ragweed allergies, a spring start (March-May) allows build-up to complete before August-September ragweed season. For perennial allergens like dust mites, pet dander, and indoor mold, there is no seasonal constraint — start whenever you are ready and have been evaluated by your allergist. The principle is consistent: pre-seasonal initiation allows you to reach your therapeutic maintenance dose before peak exposure, maximizing first-season protection. Waiting until you are already symptomatic is the most common timing mistake — shots will not provide relief for that same season.

Starting allergy shots during active spring pollen season is not contraindicated but comes with tradeoffs. Some allergists prefer to wait until after peak season to minimize the risk of heightened local and systemic reactions during the already-reactive period. Others will begin during the season with a more conservative dose escalation schedule. Either way, you should expect that starting in spring provides little to no relief for the current season — you will be in the early build-up phase while symptomatic, and most benefit develops over 3-12 months of treatment. If you are determined to start now despite being in-season, ask your allergist about cluster or rush build-up protocols that can accelerate your progression to maintenance dose. Also confirm whether your symptoms during build-up can be managed with antihistamines or nasal steroids alongside the injection schedule.

Most patients begin noticing meaningful symptom improvement within 3 to 6 months after starting allergy shots, which typically coincides with approaching or reaching the maintenance dose. Some patients report partial benefit earlier — in months 1-2 — while others do not notice significant change until the second full allergen season on maintenance. The research baseline: meta-analyses demonstrate a 33% reduction in rhinitis symptom scores and a 36% reduction in rescue medication use, but these are average figures across treated allergen seasons — individual responses vary. Children and younger adults often respond more quickly and completely than older adults. Setting realistic expectations is important: allergy shots are not like antihistamines that work within hours. The immune modification process is gradual, and benefit accumulates over many months of consistent treatment.

Allergy shots are recommended at step 4 of the standard stepped care approach — after at least one full season of optimized pharmacotherapy has failed to achieve adequate symptom control. The ARIA guidelines (Brozek et al., JACI, 2017) define this failure threshold as: daily antihistamine plus intranasal corticosteroid used consistently throughout the allergy season, with symptoms remaining moderate-to-severe. If you are still experiencing significant rhinitis symptoms, sleep disruption, or activity limitation despite this regimen, your allergist will likely recommend immunotherapy. Patients whose symptoms are well-controlled with minimal medication may not have reached the threshold where immunotherapy provides additional benefit over continued pharmacotherapy. The stepped care conversation is also the right time to discuss whether allergy testing has confirmed the specific IgE-mediated triggers that need to be addressed in the immunotherapy formula.

Yes — earlier initiation of immunotherapy in children provides stronger disease-modifying benefits than starting later. The PAT study (Moller et al., JACI, 2002) enrolled children aged 6-14 and demonstrated a 50% reduction in new asthma development over 10 years compared to pharmacotherapy-only controls. The disease-modification window is most impactful before the allergic march progresses from rhinitis to asthma. Children who show allergic rhinitis and have a family history of asthma are particularly strong candidates for early immunotherapy initiation. The minimum age is generally 5 years, determined by the child's ability to communicate symptoms and cooperate with injections and the observation period. Starting at age 5-8 when rhinitis first appears, rather than waiting until teenage years or adulthood, maximizes the opportunity to interrupt progression to more serious disease.

Allergy shots should not be initiated during pregnancy. AAAAI and ACAAI practice parameters are clear on this point: initiating immunotherapy or increasing doses during pregnancy is not recommended because systemic reactions requiring epinephrine could affect the fetus. However, if you are already in the maintenance phase of allergy shots and become pregnant, you can generally continue at your current maintenance dose — most allergists recommend continuing rather than stopping, as the benefit of ongoing treatment outweighs the risk of a reaction at a stable, well-tolerated dose. The prohibition is specifically against starting new treatment or escalating doses during pregnancy. If you are planning to become pregnant, consider timing immunotherapy initiation to reach the stable maintenance phase before conception, so you can safely continue throughout the pregnancy. Discuss your specific situation with both your allergist and your obstetrician.