Allergy Shot Ingredients: Every Component Explained by FDA Category
An allergy shot contains four ingredient categories per FDA CBER and Cox 2011 PP3: (1) allergenic extract — the active ingredient, proteins from FDA-licensed pollens, mites, danders, or venoms; (2) diluent — most commonly 50% glycerin, sometimes normal saline; (3) 0.4% phenol preservative — thimerosal is largely phased out; (4) buffer salts where present. The FDA standardizes 19 extracts; all others use PNU or w/v labeling. No blood, no live organisms, no mRNA, no adjuvants.
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Allergy shots contain allergenic extract proteins, a diluent (50% glycerin or saline), phenol 0.4% preservative, and buffer salts. The extract is patient-specific, built from FDA-licensed source materials matching your IgE sensitization profile.
The essentials
An allergy shot is not a mystery preparation. Every ingredient is listed on the FDA-licensed product package insert, and the four-category breakdown is consistent across virtually all US allergen immunotherapy products: active ingredient, diluent, preservative, and where applicable, buffer salts.
Curex's at-home IgE testing identifies the exact allergens driving symptoms — the clinical input that determines which FDA-licensed extracts would be combined into a patient-specific immunotherapy formulation.
The active ingredient is an allergenic extract — per FDA CBER, "injectable allergen extracts are sterile liquids that are manufactured from natural substances (such as molds, pollens, insects, insect venoms, and animal hair)." The allergenic activity resides in proteins and glycoproteins. The FDA maintains national reference standards for 19 standardized extracts, ensuring lot-to-lot potency consistency. Everything else is non-standardized and labeled by PNU/mL (Protein Nitrogen Units) or weight-to-volume ratio (w/v).
The 19 FDA-standardized extracts per CBER are: short ragweed (potency by Amb a 1), cat hair and cat pelt (Fel d 1), eight grass pollens (Bermuda, Kentucky/June Bluegrass, Meadow Fescue, Orchard, Perennial Rye, Redtop, Sweet Vernal, Timothy), two house dust mites (Dermatophagoides farinae and Dermatophagoides pteronyssinus), and five Hymenoptera venoms (honey bee, yellow jacket, yellow hornet, white-faced hornet, and wasp/mixed vespid).
The diluent is most commonly 50% glycerin, which serves dual purposes: it preserves allergen protein potency and is bacteriostatic at concentrations above 20%, per the AAAAI extract-preparation manual. Normal saline (0.9% sodium chloride) is used as an alternative, often with phenol added. Human serum albumin (HSA)-containing diluent at approximately 0.03% is used for very dilute aliquots to prevent allergen adsorption to glassware.
The preservative is 0.4% phenol in modern US practice. Thimerosal, the mercury-containing preservative used in older formulations, has been largely phased out per current ACAAI/AAAAI guidance. The AAAAI extract-preparation manual specifies that dilutions must be bacteriostatic: phenol ≥0.25% or glycerin ≥20%.
What allergy shots do NOT contain is equally important: no blood serum, no viral or bacterial pathogens, no live attenuated organisms, no mRNA, no genetic material, and no adjuvants of the type used in infectious-disease vaccines. Alum-adjuvanted extracts exist in some European products (e.g., Alutard) but are not standard in current US FDA-licensed aqueous extracts.
How allergy shots retrain your immune system
The four ingredient categories each serve a specific function in the immunotherapy formulation. The allergen extract provides the antigenic proteins that drive immune tolerance; the diluent stabilizes those proteins and enables precise dose escalation from 0.05 mL to 0.5 mL across the build-up phase; the preservative maintains sterility across the multi-dose vial's lifespan; and buffer salts maintain pH stability where required. Together they create a preparation that is pharmacologically inert except for the allergen proteins — which is by design: the immune response is generated by the allergen content alone.
Allergenic Extract — The Active Ingredient
Proteins and glycoproteins from FDA-licensed natural source materials. 19 extracts standardized by FDA CBER with national reference standards (BAU, AU, or major allergen µg); all others non-standardized (PNU or w/v). Potency methods per Cox 2011: total protein for venoms, radial immunodiffusion for dominant allergens (Amb a 1, Fel d 1), ID50EAL bioequivalence for grasses and mites.
Diluent — 50% Glycerin or Normal Saline
50% glycerin preferred: bacteriostatic at ≥20%, preserves allergen protein potency. Normal saline 0.9% alternative, usually with phenol. HSA diluent (~0.03% in buffered saline) for very dilute aliquots. Per AAAAI manual, bacteriostatic threshold requires phenol ≥0.25% or glycerin ≥20%.
Preservative — Phenol 0.4%
Standard antimicrobial preservative across most US extracts. Thimerosal largely phased out per ACAAI/AAAAI guidance. Phenol/glycerin combination covers both antimicrobial and stabilization requirements. Patients with phenol sensitivity should disclose this before vial preparation.
What Allergy Shots Do NOT Contain
No blood serum or plasma. No live or attenuated organisms. No mRNA or genetic material. No alum adjuvants (US aqueous standard). No latex in the extract itself — though vial stoppers historically varied; modern FDA-licensed products are largely latex-free. No egg proteins in modern US aeroallergen extracts.
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See if at-home shots are right for youFrequently asked questions
What are the four main ingredients in an allergy shot?
The four ingredient categories in every US allergy shot per FDA CBER and Cox 2011 PP3 are: (1) allergenic extract — the active ingredient, consisting of proteins and glycoproteins from FDA-licensed source materials such as pollens, dust mites, danders, molds, and Hymenoptera venoms; (2) diluent — most commonly 50% glycerin, sometimes 0.9% normal saline with phenol; (3) preservative — 0.4% phenol is the modern standard, with thimerosal largely phased out; (4) buffer salts where present for pH stability. The specific allergen content is patient-specific, built from the allergens identified in IgE testing. These four categories are listed on the package insert of every FDA-licensed allergen extract product.
Is there mercury in allergy shots?
Thimerosal — the mercury-containing preservative historically used in some allergen extract products — has been largely phased out from US allergen immunotherapy practice per current ACAAI/AAAAI guidance. Modern US practice uses phenol/glycerin bacteriostatic systems. "Largely phased out" means most current products do not contain thimerosal, but specific product formulations vary. To confirm whether a particular extract product contains thimerosal, patients should request the package insert from their allergist. Every FDA-licensed allergen extract has a package insert listing all preservatives by name and concentration. If thimerosal elimination is a priority, confirm with your allergist before the vial is prepared.
Do allergy shots contain live organisms or mRNA?
No. Allergy shots contain no live or attenuated organisms, no bacterial pathogens, no viral material, and no mRNA or genetic material of any kind. Per FDA CBER, injectable allergen extracts are sterile liquids manufactured from natural substances — specifically the protein and glycoprotein fractions of source materials such as pollens, insect venoms, and animal danders. These are protein preparations, not biological agents capable of replication or gene expression. This distinction is clinically important: allergy immunotherapy works through a protein-driven immune tolerance mechanism, not through infection or genetic modification. The concern is sometimes raised by patients who confuse allergen immunotherapy with infectious-disease vaccines.
Is there an adjuvant in US allergy shots?
No adjuvant of the type used in infectious-disease vaccines (such as aluminum salts/alum) is standard in current US FDA-licensed aqueous allergen extracts. Alum-adjuvanted extracts exist in some European products such as Alutard (ALK-Abelló), where alum prolongs depot antigen release; these have a different pharmacokinetic profile from standard aqueous extracts. US allergy practice relies on conventional aqueous extracts without alum. If a patient is receiving a depot or modified adjuvanted formulation, the package insert will specify. Standard US SCIT does not require adjuvants because the subcutaneous route itself delivers antigen to the desired antigen-presenting cell populations at an immunologically favorable rate.
Are there latex or egg proteins in allergy shots?
The allergenic extract itself does not contain latex or egg proteins. However, the vial stopper or syringe components in some older products historically contained latex. Modern FDA-licensed allergen extract products are largely latex-free, but latex-allergic patients should verify with the specific manufacturer before their vial is prepared, since latex allergy can be serious and cross-reaction risk exists. Egg proteins are not present in modern US aeroallergen extracts — the historical egg-protein concern relates to certain influenza vaccines with egg-based production systems, which is a completely separate product class from allergen immunotherapy extracts.
Can I get a list of exactly what is in my personal allergy shot vial?
Yes. You are entitled to request the package insert for each FDA-licensed extract product used in your formulation, which lists all ingredients. For the multi-allergen patient-specific vial prepared at the clinic, the allergist or compounding pharmacy maintains preparation records documenting the specific lot numbers, extract concentrations, mixing ratios, diluent, preservative, and beyond-use date. These records are part of your medical chart and are accessible to you. Per AAAAI preparation guidance, each vial should be labeled with patient name, two patient identifiers, allergen composition, lot numbers, beyond-use date, and dilution indicator. Requesting this information before treatment begins is a standard patient safety practice.
Why does the same allergen sometimes have different standardization units?
Standardization units differ because different potency-determination methods were developed at different times for different allergen categories. BAU/mL (Bioequivalent Allergy Units) are assigned via the ID50EAL intradermal bioequivalence method to standardized grass pollens, ragweed, and cat hair. AU/mL (Allergy Units) are assigned to cat pelt and house dust mites using an older bioequivalence reference. Micrograms of major allergen apply to ragweed (Amb a 1), cat (Fel d 1), and Hymenoptera venoms. Non-standardized extracts use PNU/mL or w/v. Per FDA labeling, BAU and AU are not interchangeable — they reflect different calibration standards and cannot be directly substituted. This means a vial labeled as 10,000 BAU/mL is not equivalent to one labeled 10,000 AU/mL even if they sound similar.
Is the allergy shot formulation the same for every patient?
No — the allergen composition is entirely patient-specific. The allergist designs the formulation based on the patient's IgE sensitization profile as determined by skin prick testing or serum-specific IgE testing. Only allergens confirmed as clinically relevant to the patient's symptoms are included. Multi-allergen vials are common in the US, and Cox 2011 (Summary Statement 72) notes that while studies on multi-allergen efficacy have conflicting results, the practice is widespread. High-protease extracts such as mold and dust mite are typically kept in separate vials from labile pollen allergens per AAAAI mixing guidance. The diluent, preservative, and buffer components are standardized; only the allergen content differs between patients.
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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.