Allergen Immunotherapy: The Long-Term Path to Allergy Relief
Most allergy treatments — antihistamines, nasal sprays, eye drops — treat the symptoms of allergies. Allergen immunotherapy (AIT) is different: it's the only treatment that targets the underlying immune response itself, with the goal of achieving long-lasting tolerance to specific allergens.
How Immunotherapy Works
Immunotherapy works by gradually exposing the immune system to increasing amounts of an allergen. Over time, this "retrains" the immune system to respond less aggressively to that substance. Several immune mechanisms are involved:
- Shift from allergy-promoting IgE antibodies toward protective IgG4 antibodies
- Increased activity of regulatory T-cells that dampen allergic responses
- Reduction in mast cell and basophil reactivity
Effective immunotherapy can reduce symptom severity, decrease medication needs, prevent the development of new allergen sensitivities, and lower asthma risk in allergic rhinitis patients.
Subcutaneous Immunotherapy (SCIT) — Allergy Shots
The traditional and most studied form of immunotherapy. Allergen extracts are injected under the skin of the upper arm in a two-phase process:
Build-Up Phase
Weekly injections with gradually increasing allergen doses over approximately 3–6 months (conventional schedule) or as few as 3 days (rush protocols under close supervision).
Maintenance Phase
Once the target dose is reached, injections continue monthly for 3 to 5 years. Long-term benefits often persist years after stopping treatment.
Suitable for: Allergic rhinitis, allergic asthma, insect venom allergy, some cases of atopic dermatitis.
Consideration: Requires clinic visits; small risk of systemic reaction — patients wait 20–30 minutes post-injection for observation.
Sublingual Immunotherapy (SLIT) — Drops or Tablets
SLIT delivers allergen extracts under the tongue, where specialized immune cells in the oral mucosa initiate the tolerization process. It comes in two forms:
SLIT Drops
Liquid allergen extracts placed under the tongue daily. Widely used in Europe and many other regions. Can address multiple allergens simultaneously. Administered at home after an initial supervised dose in clinic.
SLIT Tablets
Standardized, FDA/EMA-approved tablet formulations available for specific allergens, including grass pollen, house dust mite, and ragweed. Highly convenient and consistent dosing. First dose taken under medical supervision; subsequent doses taken at home.
SCIT vs. SLIT: Key Comparison
| Feature | SCIT (Shots) | SLIT (Drops/Tablets) |
|---|---|---|
| Route | Injection (clinic) | Under tongue (home) |
| Convenience | Regular clinic visits required | Daily at-home dosing |
| Evidence base | Extensive (decades of data) | Strong and growing |
| Risk of reaction | Low but requires observation | Very low |
| Multi-allergen use | Yes | Limited (tablets are single-allergen) |
| Duration | 3–5 years | 3–5 years |
Who Is a Good Candidate for Immunotherapy?
Immunotherapy is generally recommended for patients who:
- Have moderate to severe allergic rhinitis not well controlled by medication
- Experience significant side effects from allergy medications
- Want to reduce long-term reliance on daily medication
- Have been diagnosed with allergic asthma triggered by specific allergens
- Have had a severe reaction to insect stings
Immunotherapy is not typically recommended for food allergy (outside of clinical trials for specific protocols), severe or unstable asthma, or patients on certain immunosuppressive medications. An allergist will evaluate your full clinical picture before recommending it.
Realistic Expectations
Immunotherapy is not a quick fix. Most patients notice gradual improvement over the first year, with maximum benefit reached by year two or three. Completing the full recommended course significantly improves the chances of long-lasting results even after treatment ends. Discuss your specific allergens, lifestyle, and treatment goals with a qualified allergist to determine which form of immunotherapy — if any — is right for you.