Allergy & Immunology CPT and ICD Codes: Full Reference

Allergy and immunology coding is where “small” documentation gaps turn into big denials. One missing clinical trigger, one vague diagnosis, one bundled test you did not separate correctly, and you lose the claim or invite an audit. This reference is built for coders and billers who want clean, defensible CPT and ICD coding for allergy testing, asthma workups, immunotherapy, and complex reactions, without guessing.

You will get a usable code map, denial proof documentation checkpoints, and claim building workflows you can apply immediately, plus a payer ready mindset pulled from real RCM pain points and the compliance reality coders face today.

1. How Allergy & Immunology Coding Breaks (and Where Revenue Leaks)

Allergy and immunology claims fail for predictable reasons, and if you track them like a denial analyst, you will stop repeating the same mistakes. The first failure point is diagnosis precision. “Allergy” is not a diagnosis that supports medical necessity. You need a defensible problem list and symptom story that matches the service you billed, especially when you are also trying to protect downstream risk under payer rules that keep tightening under Medicare and Medicaid policy pressure discussed in this guide to future Medicare and Medicaid billing regulations and the broader regulatory changes affecting medical billing. The second failure point is testing bundling. Payers scrutinize allergy skin tests, pulmonary function testing, and evaluation and management coding in the same visit. If you cannot show what was evaluated, why it mattered, and why the test was medically necessary, the payer will treat it as routine or preventive and deny.

The third failure point is extract and immunotherapy workflows. Allergen extract preparation, build up, and injections are high touch, but payers frequently question frequency, clinical response, and adherence to protocol. If your team does not document response tracking, reaction grading, dose adjustments, and precise units, you are building a denial pipeline. Treat your immunotherapy process like an internal audit program using terminology from a real medical coding audit terms dictionary and apply compliance controls aligned with coding compliance trends. The fourth failure point is poor denial intelligence. Most teams do not read the EOB beyond the denial reason. That means they do not learn the payer’s logic, the CARC and RARC patterns, or what “proof” that payer expects. Build denial playbooks using the structure taught in this EOB reference guide and pair it with stronger reimbursement awareness from Medicare reimbursement fundamentals.

Finally, allergy coding is becoming more analytics driven. If you want to stay employable and promotion ready, you need a coder’s version of KPI thinking, the same mindset shown in predictive analytics in medical billing and the skill stack discussed in future skills for coders in the age of AI. That matters because payer edits are not random. They are patterns, and patterns can be anticipated and prevented.

Allergy & Immunology Coding Map: High-Value CPT/HCPCS + ICD-10 Pairing (Denial-Proof)

Service Bucket	Common CPT/HCPCS	ICD-10-CM Examples That Usually Support It	Documentation Must-Haves (What Payers Look For)
New patient E/M	99202–99205	J30.1, J45.909, L50.9	Problem-focused history, exam elements tied to symptoms, decision making, plan
Established patient E/M	99212–99215	J30.9, J45.40, T78.40XA	Interval change, response to therapy, med management, escalation rationale
Skin prick testing	95004	J30.1–J30.9, L50.0, Z91.010	Triggers, failed conservative tx, medication washout, panel count, reaction interpretation
Intradermal testing	95024	J30.9, T63.4XXA, Z91.030	Reason prick insufficient, venom suspicion, graded response, safety precautions
Food challenge (physician supervision)	95076, 95079	Z91.010, T78.00XA	Protocol, baseline assessment, timed dosing, reaction grading, stop criteria
Patch testing	95044	L23.9, L25.9	Exposure story, distribution, prior therapy failure, reading schedule
Spirometry	94010	J45.20–J45.998, R06.02	Indication, pre-test status, interpretation, impact on plan
Bronchodilator response	94060	J45.909, R06.2	Pre/post values, drug administered, interpretation and diagnosis confirmation
Pulse oximetry	94760	J45.901, R09.02	Medical necessity, result, how it changed treatment decision
Nebulizer treatment (when appropriate)	94640	J45.901, R06.02	Acute indication, medication, response, vitals monitoring
Allergy immunotherapy injection (single)	95115	J30.1–J30.9	Dose, vial, route, observation time, local/systemic reaction documentation
Allergy immunotherapy injection (multiple)	95117	J30.1–J30.9	Number of injections, separate sites, observation, reaction grading
Allergen extract preparation (multi-antigen, per dose)	95165	J30.1–J30.9	Mix log, total doses, stability/BUD, antigen list, medical necessity for build-up
Venom immunotherapy (as applicable)	95145–95149 (varies)	T63.4XXA, Z91.030	Systemic reaction history, test confirmation, protocol, emergency preparedness
Anaphylaxis encounter support (diagnosis pairing)	(Dx-driven)	T78.2XXA, T78.0XXA	Trigger, timing, systems involved, treatment, discharge plan, education
Urticaria evaluation	(E/M driven)	L50.0–L50.9	Duration, photos, triggers, medication history, response to antihistamines
Angioedema evaluation	(E/M driven)	T78.3XXA	Airway risk, med review (ACE inhibitors), recurrence pattern, plan escalation
Drug allergy evaluation	(visit + testing as appropriate)	Z88.0–Z88.9, T78.40XA	Index reaction details, timing, severity, alternative agents, testing rationale
Allergic rhinitis management	(E/M + testing)	J30.1–J30.9	Seasonality, triggers, failed OTC therapy, quality-of-life impairment
Asthma severity tracking	(E/M + spirometry)	J45.20–J45.998	Severity/Control, exacerbation frequency, med adherence, triggers
Atopic dermatitis allergy workup	(E/M + patch testing when indicated)	L20.9, L23.9	Distribution, exposures, failed therapy, contact trigger suspicion
Venom allergy evaluation	95024 (when used), immunotherapy codes	T63.4XXA, Z91.030	Systemic reaction description, emergency care history, prevention plan
Food allergy counseling visit	E/M levels as supported	Z91.010, T78.0XXA	Avoidance plan, emergency plan, cross-contact risks, documentation of prior reactions
Chronic cough allergy assessment	E/M + spirometry as needed	R05.3, J30.9, J45.909	Differential, triggers, response to trials, test rationale and interpretation
Allergic conjunctivitis support	Visit based	H10.1	Symptoms, triggers, treatment plan, link to rhinitis when relevant
Allergy testing interpretation	(Included in testing code)	Dx dependent	Positive/negative results, clinical relevance, how results changed plan
Vaccine reaction history coding	Dx driven	T50.Z95A (as applicable)	Reaction details, timing, components suspected, future precautions
Allergy driven sinus symptoms	Visit based	J30.9, J01.90	Duration, fever/purulence, response to therapy, allergy trigger link
Biologic therapy administration (payer specific)	Varies by drug and setting	J45.50, L20.9 (as applicable)	Prior auth, criteria met, dosing, monitoring, response tracking
Telehealth allergy follow-up (payer rules)	E/M + appropriate POS/modifiers	Dx dependent	Location, modality, consent, medical decision making, payer telehealth requirements
Denial prevention checkpoint	(Workflow)	Dx + CPT pairing	Match complaint to diagnosis, test to indication, and plan to results

2. ICD-10-CM Diagnosis Coding: Fast, Defensible Allergy Problem Lists

In allergy and immunology, the ICD-10 code is not a formality. It is the payer’s “why,” and it is also the anchor your documentation must defend. Start by building a structured diagnostic hierarchy instead of throwing generic codes onto the claim. For rhinitis, split allergic rhinitis from nonallergic patterns. For asthma, choose a code that reflects severity and status, because “unspecified asthma” repeatedly triggers downcoding and medical necessity flags when paired with spirometry or biologic planning. When symptoms are the main story, use symptom codes with intent, then convert to a definitive diagnosis as soon as the provider has enough evidence, just like you would track diagnosis evolution in the kind of structured coding mindset used in ICD-11 respiratory disease coding and other specialty references such as ICD-11 neurological disorder coding.

Use strong ICD-10 categories that routinely appear in allergy work:

• Allergic rhinitis: J30.1, J30.2, J30.9 and related codes when supported.

• Asthma: J45 category codes based on severity and complication status.

• Urticaria: L50 category codes, including allergic urticaria vs chronic idiopathic patterns when documented.

• Anaphylaxis and severe reactions: T78.2 and T78.0 series when a clear trigger exists, paired with encounter timing.

• Angioedema: T78.3 series when swelling pattern and risk level are documented.

• Contact dermatitis: L23 and related categories when exposures are clear.

• Personal history of allergy: Z91.01 and related history codes when they are supporting context, not the only “why.”

A high impact workflow is to force every diagnosis to answer two questions in the chart. What is the suspected trigger or mechanism, and what is the clinical impact. Impact is what pays. It is the reason a patient is not just “itchy,” but impaired in sleep, work, sports, or at risk of severe reactions. That’s the same level of defensibility you would aim for when you prepare for audits using coding audit terminology and when you align your approach with coding compliance trends.

Another denial driver is overusing “history of allergy” codes as primary diagnoses. Payers often treat them as background only. Use them to support risk and patient counseling, but anchor the claim on the active problem. If you are doing a food challenge, the diagnosis should clearly reflect suspected food allergy, prior reaction pattern, and the clinical reason for supervised testing. If you are doing patch testing, the diagnosis should reflect dermatitis with plausible exposure and a failure of standard therapy. If you are performing spirometry, the diagnosis must reflect asthma or a symptom set like dyspnea or wheeze that the provider is actively evaluating, and your billing team should understand how that works across specialties by studying other CPT denial prone areas like emergency medicine CPT coding and radiology CPT coding references.

Finally, do not ignore payer behavior. Denials are often rooted in policy logic, not coder logic. Track which payers reject certain allergy diagnoses for testing, and build payer specific diagnosis sets the way denial teams build playbooks using EOB interpretation and reimbursement discipline from Medicare reimbursement reference.

3. CPT and HCPCS Procedure Coding: Testing, Spirometry, Immunotherapy, and High-Risk Visits

Allergy and immunology CPT coding is not “memorize codes and bill them.” It is matching service intent with method, unit logic, and payer expectations. The CPT family for allergy testing splits by technique and purpose. Skin prick testing, intradermal testing, patch testing, and physician supervised oral food challenges each represent different resources and risk. If your claim does not clearly show why one type was chosen over another, payers often treat it as redundant or unnecessary. When you bill skin testing, ensure you can support panel counts, extracts used, interpretation, and how results changed management. That “results changed plan” language is a powerful medical necessity bridge, and it is the same claim defensibility mindset used in high scrutiny areas like cardiology CPT coding and gastroenterology CPT coding.

Pulmonary testing overlaps with allergy clinics because asthma and allergic triggers often coexist. Spirometry, bronchodilator response testing, and related measures are commonly billed, but they are also commonly challenged when the documentation does not clearly state why the test was needed today. If a patient is stable, payers may view testing as routine. Your chart must show the clinical question. Are we confirming diagnosis, assessing control, adjusting meds, or evaluating a flare. This is where coders who understand policy evolution will outperform coders who just follow habit. Track this with the future proof mindset outlined in AI in revenue cycle management and future skills in the age of AI.

Immunotherapy injection coding is a workflow problem, not just a code selection problem. The injection code is tied to what happened clinically. Was it one injection or multiple. Was there an observation period. Was there a local or systemic reaction. Was the dose held, reduced, or escalated. Was the vial changed. Many denials are caused by missing reaction and dosing documentation. Extract preparation is even riskier. Payers may deny if your mix log is weak or if units do not align with policy. You want your process to survive audit language and payer policy shifts described in coding compliance trends and broader regulatory changes.

Evaluation and management coding is still a major revenue driver in allergy clinics, and it is still a denial target. The safest approach is to document the clinical complexity you actually managed: multiple problems, medication management, flare evaluation, and risk counseling. Tie the visit to a specific clinical decision, not a generic “follow up.” If you are also doing tests, clearly separate the decision making from the test itself to reduce bundling edits. This is exactly where coders who master denial patterns through EOB analysis and claim building discipline from accurate modifier application become the people who get promoted into lead roles like those described in the director of coding operations roadmap.

One more reality: technology is changing payer edits faster than most coders update their mental playbooks. If you want to avoid being blindsided by new claim checks, follow the strategic direction discussed in predictive analytics in medical billing and the longer trend arc in the future of medical coding with AI.

Quick Poll: What’s your biggest blocker in Allergy & Immunology coding?

Pairing allergy testing CPT codes with defensible ICD-10 diagnoses so payers don’t deny “medical necessity”. Preventing bundling and modifier edits when E/M, testing, and spirometry happen in the same visit. Immunotherapy and extract billing: tracking vials, doses, reactions, and payer rules without missing units. Turning EOB denial codes into repeatable appeal packets and payer-specific prevention checklists. Keeping up with automation and analytics changes without risking compliance or audit exposure.

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4. Documentation and Medical Necessity: What Prevents Denials in Allergy Clinics

If you want fewer denials, stop thinking like a coder for a moment and think like a payer auditor. The payer asks, what was wrong, what was suspected, what was tried, and why was this test or service necessary right now. “Allergies” is not a story. A good story is “seasonal symptoms with sleep disruption, persistent despite OTC therapy, suspected pollen trigger, now testing will guide targeted immunotherapy and medication strategy.” That story supports both diagnosis and CPT coding, and it reduces the payer’s ability to label your service as exploratory.

For allergy testing, medical necessity is strongest when the provider documents impact and failed conservative management. Document that symptoms interfere with daily function, that empiric treatment did not solve it, and that identification of specific allergens will change management. If you bill patch testing, document exposure suspicion and dermatitis pattern. If you bill oral food challenges, document prior reactions, uncertainty of trigger, and why supervised challenge is the safest clinical pathway. Coders who learn to enforce these documentation rules become the people who can run denial prevention programs using EOB denial logic and policy awareness from Medicare reimbursement principles.

For spirometry and bronchodilator response tests, the documentation must state the clinical question. Do not accept “asthma follow up” as your only indication. You need changes in symptoms, concern for poor control, suspected misdiagnosis, medication escalation decisions, or evaluation of an exacerbation. Tie the results to a plan change. That “interpretation plus plan impact” is a denial resistant pattern, and you can see similar thinking across other procedure heavy specialties in cardiology CPT coding and radiology CPT references.

For immunotherapy injections and extracts, documentation is operational. You want a repeatable template that captures dose, vial, route, observation, reaction, and next step. Every time that template is incomplete, your revenue becomes optional. This is also where compliance risk lives. You are billing repetitive services with high volumes, and payers expect tight internal controls. Align your templates with concepts from the coding audit terms dictionary and implement them the way modern teams do under pressure from coding compliance trends.

Finally, do not let documentation become “more text.” Make it more proof. Proof is specific triggers, objective findings, and plan changes tied to results. That is the same mindset behind being future ready under AI in RCM and building skills described in future coder skills. The coder who can translate clinical reality into payer proof becomes invaluable.

5. Modifier and Bundling Strategy: How to Build Allergy Claims That Survive Edits

Allergy clinics are bundling magnets. E/M, testing, spirometry, and treatment often happen together, and payers will try to compress the claim. Your job is not to “force payment.” Your job is to structure the claim so the payer cannot logically deny the separate work. Start by understanding which services are inherently included and which require separation through distinct documentation and correct modifier usage. Master this skill with the same discipline taught in maximizing revenue through accurate modifier application, because that single capability is what separates average coders from denial proof coders.

When E/M and testing happen the same day, your documentation must show that the E/M was a separately identifiable service. The provider must evaluate, make decisions, and create a plan beyond the act of performing the test. If the visit is only “review symptoms and test,” payers will bundle or downcode. This is why denial prevention programs must include structured provider education. If you want a career path into leadership, this exact process is part of the skill set described in the director of coding operations roadmap.

Use denial analytics like a discipline, not a reaction. Each payer has patterns. One payer denies allergy testing without explicit failed therapy documentation. Another denies spirometry without explicit symptom change. Another flags repeated immunotherapy claims without reaction tracking. Convert these into payer specific checklists, and validate them against what the payer is telling you in the EOB. Then link your checklist priorities to policy shifts under future Medicare and Medicaid billing regulations and upcoming regulatory changes.

You also need a coder’s view of automation. Not because automation replaces you, but because automation controls claim edits and denial logic. The teams that win are the teams that treat edits like models you can predict, which is exactly what is discussed in predictive analytics in medical billing and in the strategic overview of the future of medical coding with AI. When you combine modifier discipline, documentation proof, and denial intelligence, your allergy claims stop being “hopeful.” They become engineered.

6. FAQs

• 1. What are the most common ICD-10 categories used in allergy and immunology claims?

  Most allergy clinics rely heavily on allergic rhinitis codes (J30 category), asthma codes (J45 category), urticaria codes (L50 category), anaphylaxis and severe reaction codes (T78 category), angioedema (T78.3), contact dermatitis (L23 and related), and history or status codes such as Z91.01 when used as supportive context rather than the primary “why.” The key is precision and documentation alignment, especially under shifting payer expectations discussed in Medicare reimbursement references and compliance trends.

• 2. How do you defend same-day E/M plus allergy testing from bundling denials?

  You defend it by proving two separate services happened. The E/M must include distinct evaluation, clinical decision making, and a plan that goes beyond the test itself. The chart should show what problems were evaluated, what therapies were tried, why testing was needed now, and how results informed next steps. Then apply correct modifier logic when appropriate, using frameworks from accurate modifier application and validate denial patterns via the EOB guide.

• 3. What documentation elements do payers most often require for allergy skin testing?

  Payers commonly expect symptom impact, suspected triggers, previous therapies attempted and failed, medication washout or contraindications, the number and type of tests performed, clear interpretation, and a management plan connected to results. The strongest denial prevention phrase is that results changed treatment, such as targeted avoidance, medication strategy, or immunotherapy planning. If you want a scalable clinic workflow, treat testing documentation like an audit defense file using guidance concepts from a coding audit terms dictionary and policies described in coding compliance trends.

• 4. Why do immunotherapy and extract claims get denied even when the service was performed correctly?

  Because the billing side often lacks operational proof. Payers want dosing detail, vial tracking, observation and reaction notes, protocol compliance, and correct units. If your clinic cannot show consistent documentation for reactions and dose adjustments, the payer may treat services as repetitive and medically unnecessary. This is where denial intelligence matters. Use EOB interpretation to identify payer specific denial logic and align your process to future policy tightening discussed in future Medicare and Medicaid billing rules.

• 5. How should spirometry be documented in an allergy clinic to reduce denials?

  The chart must state the clinical question and show how results influenced management. “Asthma follow up” alone is weak. Strong documentation includes symptom change, suspected poor control, possible misdiagnosis, medication escalation decisions, or evaluation of an acute flare. Add interpretation and plan impact. Cross-train your team by learning how documentation proof works in other test heavy specialties like cardiology CPT coding and radiology CPT references.

• 6. What should a denial prevention workflow look like for allergy and immunology claims?

  A denial prevention workflow should include a payer specific checklist for diagnosis to procedure pairing, documentation must-haves per service, modifier logic guidance, and a feedback loop from denials back into provider templates. Your team should track denial reason codes and convert them into prevention rules, using the EOB guide and stronger reimbursement understanding from Medicare reimbursement fundamentals. Mature teams enhance this with analytics thinking from predictive analytics in billing.

• 7. How is AI changing allergy coding and what should coders do to stay competitive?

  AI is accelerating claim edits, denial prediction, and documentation quality checks. That means coders who only memorize codes will fall behind, while coders who can interpret denial patterns, enforce documentation templates, and understand compliance risk will become more valuable. Build skills described in future coder skills in the age of AI and stay grounded in what the industry is moving toward in the future of medical coding with AI. Pair that with airtight modifier discipline from modifier optimization to stay denial proof.