Allergy ICD-10-CM Codes

Learn billable allergy ICD-10-CM codes, symptoms, diagnosis methods, and treatment options for allergic reactions, asthma, dermatitis, and more.

By Wynona Jugueta on Aug 8, 2025.

Fact Checked by Gale Alagos.

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What are Allergy ICD-10-CM Codes?

Allergies are hypersensitive immune system responses to substances known as allergens. These reactions can affect the skin, respiratory tract, or gastrointestinal system and vary in severity, from mild symptoms like a runny nose and sneezing to life-threatening anaphylaxis. In the ICD-10-CM system, several diagnosis codes are used to document allergic conditions for accurate treatment and billing.

Here are the most commonly used allergy ICD-10 codes:

J30.9 – Allergic rhinitis, unspecified (commonly called hay fever)
L20.9 – Atopic dermatitis, unspecified
T78.40XA – Allergy, unspecified, initial encounter
Z88.9 – Allergy status to unspecified drug, medicament, or biological substance
J45.909 – Unspecified asthma, uncomplicated

Which Allergy ICD-10-CM Codes are billable?

Determining which ICD-10 codes are billable and non-specific is essential for healthcare documentation. Below are examples of billable codes often used in allergy-related care:

J30.9: Yes. This is used for hay fever or seasonal allergic rhinitis.
L20.9: Yes. This code is applied to dermatitis due to allergic conditions and has no further specifications.
T78.40XA: Yes. The code captures an unspecified allergic reaction during an initial encounter.
Z88.9: Yes. This describes allergy status to unspecified medications or biologics.
J45.909: Yes. This is used for asthma not otherwise classified, often triggered by allergens.

Clinical information

Allergies are widespread immune responses to a specific allergen or substance, and they can present with diverse symptoms and complications. Here's what clinicians should know:

Symptoms may include itching, hives, sneezing, urticaria, difficulty breathing, and gastrointestinal issues like allergic diarrhea.
Common allergens include pollen, pet dander, medications, insect stings, and food (e.g., nuts, shellfish).
Conditions like food protein-induced enterocolitis and food protein-induced enteropathy are serious allergic disorders causing chronic colitis and vomiting, especially in children.
Anaphylactic shock, unspecified, can result from severe food or medication reactions and must be treated as a medical emergency.
Diagnostic tools include skin testing, blood tests, and evaluation of chronic or acute symptoms.
Treatment involves antihistamines, allergy shots, corticosteroids, and in some cases, avoidance of specified types of allergens.

Healthcare providers may also use the following ICD-10-CM codes to classify allergic reactions, including those not elsewhere classified or due to adverse effects:

K52.2: Allergic gastroenteritis and colitis (related to food protein responses)
T78.40XS: Allergy, unspecified, subsequent encounter
T78.49XA: Other allergy, not elsewhere classified, initial encounter
T78.49XS: Other allergy, not elsewhere classified, subsequent encounter
K52.21: Food protein-induced enterocolitis syndrome (FPIES)
Y57.9: Adverse effects not elsewhere classified from drugs or substances

Synonyms include

Hypersensitivity
Allergic reaction
Sensitivity to allergens
Immune response to allergens
Allergic disorder

Commonly asked questions

Common allergy triggers include pollen, pet dander, mold, insect stings, certain foods (like nuts or shellfish), and medications. These substances provoke an immune response in sensitive individuals, leading to symptoms like sneezing, itching, or swelling.

Allergies are diagnosed through a combination of medical history, physical examination, and specialized tests such as skin prick testing or blood tests to identify specific allergens. Accurate diagnosis helps determine the cause and guide treatment planning.

Treatment options include antihistamines, corticosteroids, decongestants, and allergy shots (immunotherapy). Avoiding known allergens and managing symptoms with medications are key strategies for long-term relief and prevention of severe reactions.

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