What's in Allergy Shots? How Allergen Extracts Are Made
Allergy shots contain purified allergen extracts from biological source materials — pollen, dust mite cultures, animal dander — processed through aqueous extraction, filtration, and potency standardization. Only about 19 allergens are FDA-standardized using BAU or AU units; over 100 additional allergens use non-standardized PNU or w/v measurements. Preservatives like phenol and glycerin stabilize the extract.
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Allergy shots contain purified allergen proteins suspended in a stabilizing diluent with preservatives. The active ingredient is the allergen extract — pollen, dust mite, dander, or venom — processed to specific potency concentrations.
From Source Material to Syringe: The Allergy Shot Manufacturing Pipeline
Allergy shots contain pharmaceutical-grade allergen extracts — purified proteins derived from biological source materials such as harvested pollen, cultured dust mite bodies, and animal pelt washings. The manufacturing pipeline runs from raw source collection through aqueous extraction, filtration, glycerination or lyophilization, potency standardization, quality control testing, and final vial formulation. The result is a sterile injectable containing active allergen proteins, a preservative (phenol or glycerin), and a protein-stabilizing diluent.
Understanding what goes into a vial matters because the contents determine both the safety and efficacy of your treatment. Before any extracts are mixed, identifying your specific IgE triggers is essential — options like Curex offer at-home allergy test kits covering 40+ allergens, providing the sensitization data your allergist needs to build the right extract formulation.
A critical distinction in the US market: only about 19 allergens have FDA-standardized extracts, meaning their potency is measured in bioequivalent units (BAU or AU) validated against reference standards. The remaining 100+ available allergens use non-standardized PNU (Protein Nitrogen Units) or w/v (weight/volume) measurements without bioequivalence requirements — a difference that affects how reliably dose comparisons can be made between patients or manufacturers.
Allergy shot extracts are pharmaceutical biologics with strict manufacturing controls, but only about 19 allergens meet FDA standardization requirements — the rest rely on manufacturer-specific potency units.
How Allergen Extracts Are Processed: Step by Step
The manufacturing journey from raw biological material to finished injectable extract involves multiple specialized steps. Each step is designed to preserve allergen protein integrity while removing non-allergen contaminants and ensuring consistent potency. The three major US manufacturers — ALK-Abello, Stallergenes Greer, and Jubilant HollisterStier — control virtually the entire US allergen extract supply.
Source Material Collection
Timothy grass pollen is harvested from controlled agricultural plots; ragweed from wild-harvested plants. Dust mites (D. pteronyssinus and D. farinae) are cultivated on defined nutrient media in controlled-environment chambers. Cat extract comes from pelt washings capturing the primary Fel d 1 allergen protein from sebaceous gland secretions.
Aqueous Extraction and Filtration
Raw source material is defatted, then extracted in aqueous buffer (typically phosphate-buffered saline). The resulting solution is filtered to remove non-protein contaminants, concentrated, and assessed for total protein content. This produces a crude extract containing the allergen proteins alongside other biological material.
Potency Standardization
FDA-standardized extracts (cat, dust mite, grasses, ragweed, Hymenoptera venom) are assayed using the ID50EAL skin test method to assign BAU (Bioequivalent Allergy Units) or AU (Allergy Units). Non-standardized extracts use PNU or w/v designations without bioequivalence validation, meaning two manufacturers' 1:100 w/v products may not deliver equivalent allergen doses.
Final Vial Formulation
The standardized extract is combined with a preservative — phenol (0.25–0.4%) or glycerin (50% v/v) — and a stabilizing diluent of human serum albumin saline (HSA-saline). HSA prevents allergen protein adsorption to glass vial walls, which would reduce the active allergen dose over time. Glycerinated extracts maintain potency for approximately one year at 4°C.
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Curex's at-home allergy shots deliver the same allergen desensitization as clinic SCIT — for a flat $129/month, with no clinic visits and no facility fees.
See if at-home shots are right for youAt-Home Allergy Shots vs. Sublingual Drops: Same Extracts, Different Route
Both SCIT and SLIT use the same pharmaceutical-grade allergen extracts manufactured by the same three US suppliers. The core difference is delivery route — subcutaneous injection versus under-the-tongue administration. With Curex, the subcutaneous route is now self-administered at home as one weekly shot, with your first injection and every dose change supervised live over Zoom and a prescribed epinephrine auto-injector on hand.
| Treatment | Efficacy | Duration | Cost (5yr) | Convenience | Safety |
|---|---|---|---|---|---|
At-Home Allergy Shots (SCIT, Curex)Best | Strong evidence; 85-90% success for rhinitis; disease-modifying | 3-5 years; one weekly shot at home, then monthly | $4,000-20,000 | Self-administered at home with Curex; brief 30-min self-observation | 0.1-0.2% systemic reaction rate; self-administered at home with Curex safeguards |
Sublingual Drops (SLIT) | Comparable to SCIT for most aeroallergens; disease-modifying | 3-5 years; daily drops at home | $2,340+ at home | Taken at home daily; no clinic visits or observation periods | Anaphylaxis less than 1 per 100 million doses; local oral itching most common |
- Efficacy
- Strong evidence; 85-90% success for rhinitis; disease-modifying
- Duration
- 3-5 years; one weekly shot at home, then monthly
- Cost (5yr)
- $4,000-20,000
- Convenience
- Self-administered at home with Curex; brief 30-min self-observation
- Safety
- 0.1-0.2% systemic reaction rate; self-administered at home with Curex safeguards
- Efficacy
- Comparable to SCIT for most aeroallergens; disease-modifying
- Duration
- 3-5 years; daily drops at home
- Cost (5yr)
- $2,340+ at home
- Convenience
- Taken at home daily; no clinic visits or observation periods
- Safety
- Anaphylaxis less than 1 per 100 million doses; local oral itching most common
Curex's at-home allergy shots use the same pharmaceutical-grade allergen extracts as in-clinic SCIT, compounded into a personalized serum to USP <797> standards and prescribed by a board-certified allergist. You self-administer one weekly shot at home, with your first injection and every dose change supervised live over Zoom and a prescribed epinephrine auto-injector confirmed on hand. Plans are $129/month, all-inclusive.
See if at-home shots are right for youFrequently asked questions
Are allergy shots safe ingredients for people with severe allergies?
Allergy shots contain the same proteins that trigger your allergic reactions — that is precisely how they work. The safety comes from starting at a very low dose (most dilute vial, often 1:10,000 v/v concentration) and increasing gradually over months. This controlled exposure is why 98% of systemic reactions occur within the mandatory 30-minute post-injection observation period, allowing trained staff to intervene. The preservatives (phenol or glycerin) and stabilizer (human serum albumin) used in extract manufacturing are well-established pharmaceutical excipients with long safety records. FDA-standardized extracts provide the most reliable safety profile because their potency is validated against reference standards.
Why are only 19 allergens FDA-standardized?
FDA standardization requires that manufacturers demonstrate biological equivalency of their extract to a reference standard using validated clinical assays — specifically the ID50EAL intradermal testing method. Developing and validating these reference standards is a resource-intensive regulatory process. The FDA has prioritized the most clinically important, highest-volume allergens: cat hair, Dermatophagoides farinae, D. pteronyssinus, eight grass pollen species, short ragweed, and Hymenoptera venoms (honeybee, yellow jacket, white-faced hornet, yellow hornet, wasp). The remaining 100+ allergens — including most tree pollens, mold spores, and many animal danders — use manufacturer-specific PNU or w/v potency systems that allow market availability without formal bioequivalence validation.
What preservatives are in allergy shots?
US allergen extracts use one of two main preservative systems: phenol (0.25–0.4% concentration) as an antimicrobial agent, or glycerin (50% v/v) which acts as both an antimicrobial preservative and a protein stabilizer. Glycerin is the preferred preservative for maintenance concentration vials because it significantly extends extract shelf life — glycerinated concentrates can maintain potency for approximately one year at 4°C, whereas aqueous (phenol-preserved) extracts degrade more rapidly, especially at dilute concentrations. Most clinical allergy practices use glycerinated extracts for the maintenance vial and aqueous extracts for the dilute build-up vials. Neither preservative is present at concentrations that cause adverse reactions in the small injection volumes administered.
Do allergy shots contain steroids?
Standard US allergen immunotherapy extracts do not contain corticosteroids. This distinguishes them from some compounded preparations available in other countries, which may combine allergen extracts with dexamethasone or betamethasone to provide immediate symptom relief alongside the immunotherapy component. US extract manufacturers (ALK-Abello, Stallergenes Greer, Jubilant HollisterStier) produce aqueous allergen extracts without adjuvants or corticosteroids. The AAAAI and ACAAI strongly advise against mixing corticosteroids into allergen immunotherapy vials because the steroid component masks whether the immunotherapy is causing reactions, complicates dosing, and carries cumulative systemic steroid risks. If you have been offered an injection that provides very rapid allergy symptom relief (within days), it may be a standalone corticosteroid injection rather than allergen immunotherapy.
How long do allergy shot extracts last before they expire?
Extract shelf life depends on the formulation type and storage conditions. Glycerinated extracts (used for maintenance-concentration vials) maintain potency for approximately one year when stored at 2–8°C (standard refrigerator temperature). Aqueous extracts — more commonly used for the dilute build-up vials — degrade faster, particularly at low concentrations where protein adsorption to vial walls becomes significant; these may lose potency within weeks to months. This is why your allergist's office stores vials under refrigeration and why transporting your vials between offices requires careful cold-chain management. Human serum albumin in the diluent helps slow protein adsorption. Most practices replace patient vials on a roughly annual cycle.
What is the difference between standardized and non-standardized allergy extracts?
FDA-standardized allergen extracts have undergone rigorous biological potency validation. Their concentration is measured in BAU (Bioequivalent Allergy Units) or AU (Allergy Units), units derived from calibrated clinical skin test endpoints using validated reference standards maintained by the FDA. This means a 10,000 BAU/mL cat extract from one manufacturer delivers a biologically equivalent dose to the same unit amount from another manufacturer. Non-standardized extracts — covering the majority of available allergens including most tree pollens, mold spores, and many danders — use weight/volume (w/v) or Protein Nitrogen Units (PNU) designations without formal bioequivalence validation. A 1:10 w/v preparation from two different manufacturers may not induce equivalent allergic responses, making standardized extracts preferable when available.
Can allergy shots contain multiple allergens in one vial?
Yes — most patients receive a multi-allergen extract vial customized to their specific sensitization profile. Allergists combine 2–10 or more individual allergen extracts into a single patient-specific vial, compounded in-office or through a compounding pharmacy. However, mixing must account for potential enzymatic degradation: proteolytic enzymes naturally present in cockroach, dust mite, and certain mold extracts can break down pollen proteins when combined in the same vial. To prevent this degradation, allergists often prepare two separate vials — one containing the protease-active allergens (mites, mold, cockroach) and one containing the pollen allergens — administered in separate injections at each visit. This two-vial approach is standard practice in many allergy clinics.
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Read moreGet your allergy shots — without the clinic.
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This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about a medical condition. Content reviewed by board-certified allergists at Curex.