Are Allergy Shots Immunotherapy? The Terminology Taxonomy Explained

No — allergy shots (allergen immunotherapy) and cancer immunotherapy are fundamentally different treatments that happen to share the word 'immunotherapy.' Cancer immunotherapy (checkpoint inhibitors like pembrolizumab, CAR-T cell therapy, cytokine therapy) activates the immune system to attack tumor cells — the goal is maximum immune activation. Allergy immunotherapy calms an overreactive immune response to harmless allergens — the goal is tolerance induction. The underlying biological mechanisms are nearly opposite: cancer IT blocks inhibitory signals to unleash immune attack; allergen IT expands regulatory T cells and increases IgG4 blocking antibodies to suppress inappropriate immune reactions.

All three are forms of allergen immunotherapy (AIT) — they share the same immune mechanism but differ in how allergen is delivered. Allergy shots (SCIT) are injected subcutaneously into the upper arm, traditionally at a clinic with weekly build-up visits and monthly maintenance and a 30-minute observation period; at-home SCIT programs like Curex now let eligible patients self-inject at home, with the first dose and every dose change supervised live over Zoom. Allergy drops (SLIT-D) are liquid allergen formulations held under the tongue for 1-2 minutes and swallowed — administered at home daily. Allergy tablets (SLIT-T) are dissolvable FDA-approved tablets also held under the tongue — Grastek, Ragwitek, Oralair, and Odactra are the four approved products. Drops and tablets are both forms of sublingual immunotherapy; drops treat multiple allergens in one formulation while each tablet treats only one allergen.

Leonard Noon at St. Mary's Hospital in London first injected pollen extracts subcutaneously into hay fever patients in 1911 and published the results in the Lancet — making allergen immunotherapy over 110 years old and the oldest surviving specific biological therapy in medicine. His initial rationale was a 'toxin-antitoxin' model since the immunological mechanisms were not yet understood. The modern mechanistic understanding — regulatory T cells, IgG4 blocking antibodies, immune tolerance induction — developed through research in the late 20th and early 21st centuries. The WHO endorsed the term 'allergen immunotherapy' in 1998 (Bousquet et al., JACI 1998) to standardize terminology globally and distinguish it from cancer immunotherapy.

Desensitization and tolerance are related but distinct states. Desensitization is a temporary reduction in immune reactivity that requires ongoing allergen exposure to maintain — similar to how rush food protocols for peanut allergy provide protection only as long as regular peanut consumption continues. Tolerance is a persistent immunological change that endures after allergen exposure stops. The goal of allergen immunotherapy — allergy shots and sublingual drops/tablets — is true tolerance (Burks et al., JACI 2013), not merely desensitization. This is why a 3-5 year treatment course is needed: the immune reprogramming that produces lasting tolerance takes time to establish at the level of regulatory T cell populations and B cell IgE/IgG4 ratios.

Most major US commercial insurance plans cover SCIT (allergy shots) under the specialist care benefit, typically with copays of $15-50 per visit and prior authorization requirements. Medicare Part B covers allergy immunotherapy (SCIT) at 80% of the approved amount after the deductible. SLIT tablets (Grastek, Ragwitek, Oralair, Odactra) are covered by many plans under pharmacy benefits, often with copay cards from manufacturers available for as little as $15-35 per month. Compounded SLIT drops are generally not covered by insurance because they are off-label — the allergen extracts used are FDA-approved only for injection, not sublingual use. Coverage verification before starting is strongly recommended.

The primary CPT codes for SCIT are 95165 (professional services for preparing allergen immunotherapy, per dose) and 95115 or 95117 (professional services for allergen immunotherapy — 95115 for a single injection not on the first visit, 95117 for two or more injections). Allergy skin testing uses separate codes: 95004 (percutaneous skin tests). For SLIT, there is no equivalent billing code because SLIT is dispensed as a prescription, not administered in-office. Knowing these codes helps patients verify their explanation of benefits and understand charges on their insurance statements.

Standard environmental allergen immunotherapy (SCIT or SLIT) is not used for food allergies due to the higher anaphylaxis risk with food antigens in systemic doses. However, Palforzia (peanut oral immunotherapy, FDA-approved 2020) uses a related approach for peanut allergy in patients 4-17 years old — daily escalating peanut doses taken orally under medical supervision. Research on oral immunotherapy (OIT) for other foods — milk, egg, tree nuts — is active. Sublingual immunotherapy for food allergies is an area of ongoing clinical trials but is not currently an established standard-of-care approach outside specialty research centers.