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Most allergy treatments manage symptoms. Antihistamines block histamine receptors. Decongestants reduce nasal swelling. Nasal steroids suppress inflammation. All of these are useful — but none of them address what is actually happening in your immune system. The moment you stop taking them, your immune system goes right back to reacting to the same allergens the same way.
Immunotherapy is different. It is the only treatment that can fundamentally change how your immune system responds to allergens — training it to tolerate substances it currently identifies as threats. For many people, this results in lasting symptom reduction or complete remission that continues long after the treatment course ends.
Medical Disclaimer: The information on this page is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Immunotherapy must be prescribed and supervised by a qualified allergist. Always consult a healthcare provider before starting, stopping, or changing any allergy treatment. In the event of a severe allergic reaction or anaphylaxis, call 911 immediately and use an epinephrine auto-injector if one has been prescribed.
What Immunotherapy Actually Does
When your immune system encounters an allergen — dust mite protein, cat dander, grass pollen — it identifies it as a threat and produces IgE antibodies in response. Those IgE antibodies bind to mast cells throughout your body, priming them to release histamine and other inflammatory mediators the next time that allergen reappears. That release is what produces your symptoms.
Immunotherapy works by introducing very small, controlled amounts of the allergen into your body on a regular schedule — gradually increasing the dose over time. With repeated exposure at these controlled levels, your immune system begins to produce a different type of antibody — IgG — sometimes called a "blocking antibody." IgG antibodies compete with IgE for the same allergen, essentially intercepting it before it can trigger the mast cell response.
Over time, with consistent treatment, the IgE-driven response becomes less dominant. Symptoms become less severe, less frequent, or in some cases stop occurring entirely. This is the only treatment that targets the underlying immune mechanism rather than masking the downstream effects.
Allergy Shots vs Allergy Drops — What Is the Difference?
There are two main forms of allergen immunotherapy available today.
Subcutaneous Immunotherapy (SCIT) — Allergy Shots
The traditional and most widely studied form. Small amounts of allergen extract are injected under the skin — typically in the upper arm. Because injections carry a small risk of a systemic allergic reaction, shots must be administered in a medical office, and patients are observed for 20 to 30 minutes afterward. This is a safety requirement, not a precaution that can be skipped.
SCIT is effective for a wide range of environmental allergens including dust mites, pet dander, mold, pollen, and insect venom. It has the longest track record and the most robust clinical evidence base of any immunotherapy approach.
Sublingual Immunotherapy (SLIT) — Allergy Drops or Tablets
A newer approach in which allergen extracts are placed under the tongue rather than injected. The allergen is absorbed through the mucous membranes into the bloodstream. After an initial in-office dose to confirm tolerance, many patients can take subsequent doses at home — which is a significant practical advantage for people with busy schedules or difficulty attending frequent appointments.
SLIT is FDA-approved for certain grass and ragweed pollens and dust mite allergy in tablet form. Off-label liquid drop preparations are also used by some allergists for a broader range of allergens. The evidence base for SLIT is growing, though it is generally considered somewhat less potent than SCIT for the same allergens. Your allergist can advise which approach is appropriate for your specific allergen profile and lifestyle.
The Two Phases of Immunotherapy
Phase 1 — The Build-Up Phase
Immunotherapy begins with very low concentrations of allergen — far too low to trigger symptoms — administered once or twice a week. Each subsequent dose contains a slightly higher concentration. The build-up phase typically lasts 3 to 6 months.
Many patients begin to notice improvement during this phase, particularly toward the end, when doses are approaching maintenance levels. Others take longer. The pace of the build-up is determined by your allergist based on how your immune system responds — it is not something to rush.
Phase 2 — The Maintenance Phase
Once the target maintenance dose is reached, injections shift to monthly or every-other-month intervals. The maintenance phase typically continues for 3 to 5 years. Most patients achieve their best results during this phase — as the cumulative exposure gradually shifts the immune response.
Commitment during the maintenance phase is critical. Stopping early — which is one of the most common reasons immunotherapy fails to produce lasting results — means the immune system has not had sufficient cumulative exposure to fully consolidate the tolerance it has been building. Your allergist will advise when it is appropriate to stop based on your response.
What Immunotherapy Can and Cannot Do
Immunotherapy can produce a lasting reduction in allergy symptoms — in some cases, complete remission that continues for years after the treatment course ends. It can prevent the development of sensitivity to new allergens, which is a significant benefit for people whose allergies have been expanding over time. It can reduce asthma symptoms in people with allergy-triggered asthma. For insect venom allergy in particular, it can be life-changing.
What it cannot do is guarantee results for everyone. Response varies by person, allergen type, and adherence to the treatment schedule. Some people find that shots significantly reduce but do not eliminate symptoms. A small percentage find limited benefit. This is why immunotherapy works best for people who are clearly sensitized to specific, testable allergens — confirmed through skin prick testing or specific IgE blood testing — rather than people with vague or unconfirmed allergy diagnoses.
Allergen Avoidance During Immunotherapy — Still Essential
A common misconception is that starting immunotherapy means you no longer need to worry about allergen avoidance. This is not correct — and it can undermine your results.
During the build-up and maintenance phases, your immune system actively builds tolerance. Continued high-level exposure to the allergen you are being treated for means your immune system is simultaneously fighting the very thing it is trying to learn to tolerate. Reducing your background allergen load through avoidance measures gives the immunotherapy a better environment to work in.
For dust mite allergy — one of the most common indications for immunotherapy — continuing to use allergen-proof mattress and pillow encasements, washing bedding weekly with an allergen-eliminating laundry additive, and maintaining bedroom humidity between 30 and 50% all reduce your ongoing exposure while your immune system builds tolerance. The combination of immunotherapy plus avoidance consistently produces better outcomes than either approach alone.
Our complete guide to allergy-free living covers the full range of allergen avoidance strategies for dust mites, pet dander, mold, and pollen — all relevant during immunotherapy.
The Bottom Line
If your allergy symptoms are not adequately controlled by medication, or if you want to reduce your long-term dependence on antihistamines and nasal steroids, immunotherapy is worth discussing with your allergist. It is a significant commitment — months to years, regular appointments, consistent adherence. But it is the only treatment that addresses the root cause rather than the downstream symptoms.
Talk to your allergist about whether you are a candidate, which form is appropriate for your allergen profile, and what realistic outcomes look like for your situation.
This is part of our complete guide to allergy-free living. Read the full guide →
Sources
American Academy of Allergy, Asthma and Immunology — Allergen Immunotherapy:
American College of Allergy, Asthma and Immunology — Allergy Shots