ICD-10 Code for Allergy

The default ICD-10-CM 2027 code for allergy, allergic (reaction) (to) is T78.40 – Allergy, unspecified (a header – choose a more specific code). More specific codes depend on the details documented, as listed in the official index (57 codes, 34 billable).

Main code: T78.40 – Allergy, unspecified
Billable: No – header code

Index entries for Allergy

air-borne substance NEC (rhinitis) – J30.89
alveolitis (extrinsic) – J67.9
- due to
  - Aspergillus clavatus – J67.4
  - Cryptostroma corticale – J67.6
  - organisms (fungal, thermophilic actinomycete) growing in ventilation (air conditioning) – J67.7
- specified type NEC – J67.8
anaphylactic reaction or shock – T78.2 (header)
angioneurotic edema – T78.3 (header)
animal (dander) (epidermal) (hair) (rhinitis) – J30.81
bee sting (anaphylactic shock) – T63.44- (header)
biological – see Allergy, drug
colitis – K52.29 – see also Colitis, allergic
dairy products – T78.119 (header)
- with
  - reactivity to baked milk – T78.111 (header)
  - tolerance to baked milk – T78.110 (header)
- anaphylactic reaction – T78.079 (header)
  - with
    - reactivity to baked milk – T78.071 (header)
    - tolerance to baked milk – T78.070 (header)
dander (animal) (rhinitis) – J30.81
dandruff (rhinitis) – J30.81
dental restorative material (existing) – K08.55
dermatitis – see Dermatitis, contact, allergic
diathesis – see History, allergy
drug, medicament & biological (any) (external) (internal) – T78.40 (header)
- correct substance properly administered – see Table of Drugs and Chemicals, by drug, adverse effect
- wrong substance given or taken NEC (by accident) – see Table of Drugs and Chemicals, by drug, poisoning
due to pollen – J30.1
dust (house) (stock) (rhinitis) – J30.89
- with asthma – see Asthma, allergic extrinsic
eczema – see Dermatitis, contact, allergic
eggs
- adverse reaction NEC – T78.129 (header)
  - with
    - reactivity to baked egg – T78.121 (header)
    - tolerance to baked egg – T78.120 (header)
- anaphylactic reaction – T78.089 (header)
  - with
    - reactivity to baked egg – T78.081 (header)
    - tolerance to baked egg – T78.080 (header)
epidermal (animal) (rhinitis) – J30.81
feathers (rhinitis) – J30.89
food (any) (ingested) – T78.19 (header)
- anaphylactic shock – see Shock, anaphylactic, due to food
- dermatitis – see Dermatitis, due to, food
- dietary counseling and surveillance – Z71.3
- in contact with skin – L23.6
- rhinitis – J30.5
- status (without reaction) – Z91.018
  - beef – Z91.014
  - eggs – Z91.0120
    - with
      - reactivity to baked egg – Z91.0122
      - tolerance to baked egg – Z91.0121
  - lamb – Z91.014
  - mammalian meats – Z91.014
  - milk products – Z91.0110
    - with
      - reactivity to baked milk – Z91.0112
      - tolerance to baked milk – Z91.0111
  - peanuts – Z91.010
  - pork – Z91.014
  - red meats – Z91.014
  - seafood – Z91.013
  - specified NEC – Z91.018
gastrointestinal – see also specific type of allergic reaction
- meaning colitis – K52.29 – see also Colitis, allergic
- meaning gastroenteritis – K52.29 – see also Gastroenteritis, allergic
- meaning other adverse food reaction not elsewhere classified – T78.19 (header)
grain – J30.1
grass (hay fever) (pollen) – J30.1
- asthma – see Asthma, allergic extrinsic
hair (animal) (rhinitis) – J30.81
history (of) – see History, allergy
horse serum – see Allergy, serum
inhalant (rhinitis) – J30.89
- pollen – J30.1
kapok (rhinitis) – J30.89
medicine – see Allergy, drug
milk protein – Z91.0110 – see also Allergy, food
- with
  - reactivity to baked milk – Z91.0112
  - tolerance to baked milk – Z91.0111
- adverse reaction NEC – T78.119 (header)
  - with
    - reactivity to baked milk – T78.111 (header)
    - tolerance to baked milk – T78.110 (header)
- anaphylactic reaction – T78.079 (header)
  - with
    - reactivity to baked milk – T78.071 (header)
    - tolerance to baked milk – T78.070 (header)
- dermatitis – L27.2
- enterocolitis syndrome – K52.21
- enteropathy – K52.22
- gastroenteritis – K52.29
- gastroesophageal reflux – K21.9 – see also Reaction, adverse, food
  - with esophagitis (without bleeding) – K21.00
    - with bleeding – K21.01
- proctocolitis – K52.29
nasal, seasonal due to pollen – J30.1
pneumonia – J82.89
pollen (any) (hay fever) – J30.1
- asthma – see Asthma, allergic extrinsic
primrose – J30.1
primula – J30.1
proctocolitis – K52.29
purpura – D69.0
ragweed (hay fever) (pollen) – J30.1
- asthma – see Asthma, allergic extrinsic
rose (pollen) – J30.1
seasonal NEC – J30.2
Senecio jacobae (pollen) – J30.1
serum – T80.69 (header) – see also Reaction, serum
- anaphylactic shock – T80.59 (header)
shock (anaphylactic) – T78.2 (header)
- due to
  - administration of blood and blood products – T80.51 (header)
  - adverse effect of correct medicinal substance properly administered – T88.6 (header)
  - immunization – T80.52 (header)
  - serum NEC – T80.59 (header)
  - vaccination – T80.52 (header)
specific NEC – T78.49 (header)
tree (any) (hay fever) (pollen) – J30.1
- asthma – see Asthma, allergic extrinsic
upper respiratory – J30.9
urticaria – L50.0
vaccine – see Allergy, serum
wheat – see Allergy, food

How to choose the right code

Start with the main term, then pick the indented subterm that matches the documentation (type, cause, site, laterality, episode of care). Always confirm the code in the tabular list: follow its Excludes1/Excludes2, “code first” and “use additional code” notes, and add a 7th character where required.

Source: CDC/NCHS ICD-10-CM FY2027 alphabetic index.