Allergy Immunotherapy Injections: A Step-by-Step Walkthrough

Most patients describe allergy shots as a brief, mild sting at the injection site — similar to a routine blood draw or flu shot, but generally less uncomfortable because the volume is small and the needle is fine (26–27 gauge, 0.5 inches). The subcutaneous delivery into the fatty layer of the upper arm is typically less painful than an intramuscular injection. After the initial sting, some patients notice a mild burning sensation at the injection site as the extract disperses. Local redness and swelling are common, occurring in 26–86% of patients (Tankersley et al., JACI 2000), and can range from barely noticeable to the size of a half-dollar or larger. Most patients report that discomfort diminishes as they progress through the buildup phase and their immune system adapts.

Allergy shots are given subcutaneously (under the skin) into the posterior lateral upper arm — the triceps area on the back of the arm. This location is chosen because the subcutaneous fat in this region contains the dendritic cells that absorb allergen extract and carry it to draining lymph nodes, initiating the immune tolerance process. A fine 26–27 gauge needle, typically 0.5 inches in length, is used to deliver the dose just beneath the skin without entering the muscle. Patients with bilateral sensitizations may receive injections in both arms simultaneously to accommodate multiple allergen extracts. The site is wiped clean before the injection but does not require a bandage afterward in most cases.

The 30-minute post-injection observation period is mandatory because approximately 85% of all serious systemic reactions to allergy shots occur within 30 minutes of the injection (Epstein et al., Ann Allergy Asthma Immunol 2011). During this window, the allergen is being absorbed and can trigger immediate IgE-mediated mast cell degranulation in sensitized patients. The observation requirement ensures that a trained clinician with epinephrine, oxygen, and emergency equipment is available to treat any systemic reaction before a patient leaves the building. Reactions that occur after 30 minutes are less common and tend to be less severe, but patients are advised to remain near medical care and to have a prescribed epinephrine auto-injector available for the several hours following each injection.

Allergy shots begin at a starting dose that is 1,000 to 10,000 times less concentrated than the final maintenance dose. This incremental approach uses a five-vial dilution series, where each vial is typically 10 times more concentrated than the previous one. The conventional dilution sequence runs from 1:10,000 to 1:1,000 to 1:100 to 1:10 to the full maintenance concentrate. Within each vial, the injected volume escalates from 0.05 milliliters to 0.50 milliliters across roughly six injection steps. Each 0.50 milliliter at full concentration is approximately one-tenth of a teaspoon. The purpose of this gradual escalation is to allow the immune system to build tolerance incrementally without triggering a large systemic reaction. Your allergist will advance your dose at each visit based on how you tolerated the previous injection.

After completing the mandatory 30-minute observation period at the clinic, patients are generally advised to avoid vigorous exercise for at least two hours following each injection. Intense exercise increases blood flow, which can accelerate allergen absorption and increase the risk of a delayed local or systemic reaction. Patients should also avoid alcohol, hot baths, and saunas for a few hours post-injection for similar reasons. If you notice increasing swelling, hives, runny nose, chest tightness, or any other systemic symptoms after leaving the clinic, contact your allergist immediately or go to an emergency room. Your prescribed epinephrine auto-injector should be with you at all times on injection days. Report all significant reactions to your allergist before your next scheduled injection.

Traditionally yes — the AAAAI/ACAAI Practice Parameter (Cox et al., JACI 2011) calls for SCIT injections to be given where epinephrine, personnel trained in anaphylaxis management, and emergency equipment are available, which historically meant the clinic. Telehealth SCIT programs like Curex now make at-home self-administration possible for eligible maintenance patients by reproducing those safeguards a different way: a personalized serum sterile-compounded to USP <797>, a prescribed epinephrine auto-injector confirmed on hand before the first injection, the first dose and every dose change supervised live over Zoom by the prescribing allergist, and gradual week-by-week dose escalation. Your allergist confirms candidacy and trains you first. FDA-approved SLIT tablets and drops, by contrast, require only the first dose under supervision with all later doses at home.

Most patients report that early buildup injections feel milder because the doses are very small and dilute. As the buildup progresses through higher-concentration vials, the injection site reaction tends to become more noticeable — the extract contains more allergen protein, and the local immune response at the injection site reflects this. Some patients experience a burning or stinging sensation that lasts a few minutes, followed by a growing wheal of redness and swelling over the next 15–30 minutes. Once maintenance is reached, doses stabilize and many patients find their local reactions become more predictable and often somewhat smaller as long-term immune tolerance develops. Maintenance injections at the full therapeutic dose typically produce less variability in local reactions than the escalating buildup doses.