What Is in Allergy Shots? The Complete Ingredients Guide
Allergy shots contain three main ingredient layers: purified allergen extracts (the active ingredient — proteins from pollen, dust mites, cat dander, or venom), a diluent of human serum albumin, phenol 0.4%, and normal saline, and glycerin as a stabilizer. Each vial is custom-compounded from these components based on your allergy test results. No steroids, mercury, or live organisms are included in the formulation.
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Allergy shots contain purified allergen proteins, phenol 0.4%, human serum albumin, and glycerin. Each vial is custom-mixed from your allergy test results — no steroids, mercury, or live organisms.
The Transparent Ingredient List: What Goes Into Your Allergy Shot Vial
Every allergy shot vial contains three layers of ingredients: the active component (allergen extracts — purified proteins from the environmental substances you are allergic to), the diluent that carries and stabilizes those proteins for injection, and the storage stabilizer that keeps extracts potent between clinic visits.
The active ingredient varies by patient. Your vial might contain grass pollen proteins, dust mite fecal particle proteins, cat Fel d 1, ragweed antigen E, or Hymenoptera venom — or a custom combination of several extracts selected and mixed by your allergist based on your specific allergy testing results. No two patients' vials contain exactly the same formulation.
What remains constant across virtually all allergy shot vials is the diluent and stabilizer system: human serum albumin (HSA) at 0.03% as a protein stabilizer, phenol at 0.4% as a bacteriostatic preservative, and normal saline (0.9% sodium chloride) as the carrier vehicle. Glycerin at 50% volume-to-volume concentration is added to the stock extract concentrates as a protease inhibitor and cold-storage stabilizer.
Before your allergist can select which extract proteins belong in your vial, you need comprehensive allergy testing to identify your specific IgE sensitivities. Curex at-home allergy testing measures your IgE reactivity to 40+ environmental allergens via a finger-prick blood test, giving your care team the exact data they need to design your custom formulation.
Importantly, allergy shot vials contain no steroids, no mercury (thimerosal), no aluminum adjuvants, and no live or inactivated organisms — they are not vaccines and work through an entirely different mechanism.
Allergy shots are custom-compounded biological products containing your specific allergen proteins suspended in a human serum albumin, phenol, and saline diluent. No two patients' vials are identical, and there is no single 'brand name' allergy shot.
How Each Ingredient in the Vial Serves a Specific Purpose
Every ingredient in an allergy shot vial is there for a specific, scientifically justified reason. The allergen extract proteins are the therapeutic agent — they are the only component that drives immune tolerance by exposing your immune system to controlled doses of your specific triggers. The diluent components exist to protect the proteins during storage and injection, prevent bacterial contamination, and ensure the extract can be safely delivered subcutaneously. For patients looking to benefit from this same ingredient system at home, Curex's At-Home Allergy Shot Kit uses the identical pharmaceutical building blocks — allergen extract proteins, phenol 0.4%, human serum albumin, and glycerin — sterile-compounded to USP <797> in a personalized formulation. One weekly subcutaneous shot at home for $129/month, with a board-certified allergist overseeing the plan.
Allergen Extracts — The Active Ingredient
Allergen extracts are purified proteins derived from environmental sources — pollen grains, dust mite bodies and fecal particles, animal dander and saliva, mold spores, or insect venom sacs. These are the proteins that triggered your immune system's original allergic response. When injected in precisely controlled microdoses, they progressively retrain your immune response from allergen-reactive to allergen-tolerant.
Human Serum Albumin — The Protein Stabilizer
Human serum albumin (HSA) at 0.03% prevents allergen proteins from adsorbing (sticking) to the glass walls of the vial, which would reduce the effective dose. HSA is derived from screened human plasma donors and processed to be non-infectious. Without this stabilizer, protein concentration in the vial would decrease unpredictably between uses, making dosing unreliable.
Phenol — The Bacteriostatic Preservative
Phenol at 0.4% prevents bacterial growth in multi-dose vials opened repeatedly during treatment. This is a standard preservative used in injectable medications for over a century with a well-established safety profile. The concentration used in allergy shots (0.4%) is well within limits considered safe for subcutaneous injection and is far below concentrations associated with toxicity.
Glycerin — The Extract Stabilizer
Glycerin at 50% volume-to-volume concentration in stock extract concentrates serves as a protease inhibitor, preventing enzymes naturally present in some extracts (particularly mold and cockroach) from degrading other protein extracts co-stored in the same vial. Glycerin also provides cryoprotection during cold storage, maintaining extract potency across the 12-month vial lifespan.
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See if at-home shots are right for youFrequently asked questions
Do allergy shots contain steroids?
No, standard allergy shots (subcutaneous immunotherapy) do not contain steroids. The active ingredient is purified allergen extract proteins, not corticosteroids. This is a common confusion because some patients receive Kenalog (triamcinolone acetonide) injections from their doctor for temporary allergy symptom relief — these ARE steroid shots, but they are a completely different treatment from immunotherapy. Allergy immunotherapy shots contain allergen proteins, human serum albumin, phenol preservative, saline, and glycerin. They work through immune reprogramming over 3-5 years, not through anti-inflammatory steroid activity. If your doctor mentions an 'allergy shot,' clarify whether they mean immunotherapy or a corticosteroid injection.
Are allergy shots the same as vaccines?
Allergy shots are biologically related to vaccines in that both use specific antigens to modify immune responses, but they differ in several important ways. Vaccines train the immune system to produce a protective response against pathogens (viruses, bacteria). Allergy shots train the immune system to reduce its response to environmental proteins it has incorrectly classified as threats. Allergy shots contain no live or inactivated organisms, no adjuvants (like aluminum), and no thimerosal (mercury preservative). The dosing schedule is also completely different — vaccines typically require 1-3 doses for lifelong protection, while allergy shots require 50-80 build-up injections plus years of monthly maintenance to achieve tolerance.
What are the different types of allergen extracts used in allergy shots?
Allergen extracts used in allergy shots fall into two regulatory categories. FDA-standardized extracts have consistent potency measured in Bioequivalent Allergy Units (BAU) or Allergy Units (AU) — these exist for cat hair/pelt, dust mites (D. farinae and D. pteronyssinus), eight grass pollen species, short ragweed, and Hymenoptera (stinging insect) venoms. Non-standardized extracts cover trees, most weeds (except ragweed), molds, dog, and cockroach — measured in protein nitrogen units (PNU) or weight-to-volume (w/v) ratios, which means potency can vary between lots. Major manufacturers include Greer Laboratories, ALK-Abello, and Stallergenes Greer, all FDA-licensed biological product manufacturers.
Why can't I mix all my allergens into one vial?
Some allergen combinations cannot be mixed into the same vial because certain extracts produce enzymes called proteases that degrade other protein extracts when stored together. Fungal (mold) extracts and cockroach extract are particularly problematic — they contain proteases that break down pollen and dust mite proteins. Mixing them causes the pollen or mite extracts to lose potency before they can be administered. Your allergist will separate incompatible allergens into different vials to maintain extract integrity. This is why some patients receive injections from two different vials per visit — typically one vial per arm. The AAAAI practice parameters provide specific guidance on which allergens require separation.
How long do allergy shot vials remain effective?
Mixed allergen extract vials typically expire 12 months after mixing, or earlier if stored improperly. Vials must be refrigerated at 2-8 degrees Celsius (36-46 degrees Fahrenheit) — exposure to temperatures outside this range can denature the allergen proteins and reduce their therapeutic potency. Your allergist tracks each vial's expiration date and will prepare a new vial before the previous one expires. If you miss a significant stretch of appointments and your vial expires unused, a new vial will need to be prepared. Standardized extract stock concentrates from manufacturers typically have longer shelf lives, but once mixed for patient use, the 12-month limit applies.
Is phenol in allergy shots safe?
Yes, phenol at 0.4% concentration is safe for subcutaneous injection and has been used as a bacteriostatic preservative in injectable medications for over a century. The concentration in allergy shot vials is far below levels associated with local tissue irritation or systemic toxicity. It is the same preservative used in many other injectable pharmaceutical products. Phenol prevents bacterial contamination of multi-dose vials that are accessed repeatedly during your treatment — an important safety function. Patients with known phenol sensitivity should inform their allergist, though true phenol allergy is extremely rare. The small volume injected (0.05-0.5mL) means the actual amount of phenol delivered per injection is negligible.
What is human serum albumin and is it safe?
Human serum albumin (HSA) is the most abundant protein in human blood plasma. In allergy shots, it is used at 0.03% concentration as a protein stabilizer, preventing allergen proteins from adsorbing to the glass walls of the vial. HSA used in pharmaceutical products is derived from screened human plasma donors and processed under FDA-regulated conditions to eliminate infectious disease risk, similar to other plasma-derived products like intravenous immunoglobulin. Patients with egg allergy sometimes ask about HSA safety — HSA is not related to egg proteins and is well-tolerated by patients with egg allergy. Severe albumin allergy is extremely rare and would be identified during your initial allergist evaluation.
How do I know which allergens are in my specific vial?
The allergens in your specific vial are determined by your allergy test results combined with your allergist's clinical judgment about which sensitizations are clinically relevant. Not all positive skin test or IgE blood test results automatically qualify for inclusion — your allergist evaluates whether your symptoms correlate with exposure to each allergen before adding its extract to your formulation. You can and should ask your allergist for a complete list of the extracts in your vials, including their concentrations. Most allergist offices maintain this documentation for each patient. The vials are often labeled with color codes corresponding to dilution levels, and each vial's contents are recorded in your medical chart. You have the right to know exactly what is being injected.
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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.