What is the ICD10 code for an allergic rash to Voltaren (diclofenac) gel?

ICD-10 Code for Allergic Rash to Voltaren (Diclofenac) Gel

For an allergic contact dermatitis rash from topical diclofenac (Voltaren gel), use ICD-10 code L23.3 (Allergic contact dermatitis due to drugs in contact with skin) or L25.1 (Unspecified contact dermatitis due to drugs in contact with skin). If the reaction is more severe or systemic (urticaria, angioedema, or anaphylaxis), use T88.6 (Anaphylactic reaction due to adverse effect of correct drug or medicament properly administered) or T78.40 (Allergy, unspecified) with an additional code T39.391A (Poisoning by other nonsteroidal anti-inflammatory drugs [NSAID], accidental [unintentional], initial encounter) to specify the drug 1, 2.

Primary Coding Options Based on Reaction Type

For Localized Allergic Contact Dermatitis (Most Common)

• L23.3 is the most appropriate code when eczematous lesions appear at the site of topical diclofenac application, typically appearing more than 24 hours after exposure 2
• This represents a type IV delayed hypersensitivity reaction, which is the most common presentation of diclofenac gel allergy 2
• Allergic contact dermatitis from diclofenac typically presents as intensely itchy eczematous lesions localized to application sites after several days of treatment 2

For Systemic or Immediate Reactions

• T88.6 (Anaphylactic reaction due to adverse effect of correct drug) should be used for immediate hypersensitivity reactions including urticaria, angioedema, or anaphylaxis 1, 3
• T78.2 (Anaphylactic shock, unspecified) can be used for severe anaphylactic presentations 4
• Add T39.391A as a secondary code to identify diclofenac as the causative NSAID 1

Coding Algorithm Based on Clinical Presentation

Step 1: Determine Reaction Timing and Type

• Delayed onset (>24 hours): Suggests allergic contact dermatitis → Use L23.3 2
• Immediate onset (<6 hours): Suggests IgE-mediated reaction → Use T88.6 or T78.2 1, 3

Step 2: Assess Reaction Severity

• Localized skin reaction only: L23.3 or L25.1 2
• Generalized urticaria/angioedema: T88.6 with T39.391A 1
• Anaphylaxis with systemic symptoms: T78.2 with T39.391A 3, 4

Step 3: Add Specificity

• Always include an external cause code (T39.391A for diclofenac) when using T-codes to identify the specific NSAID 1, 5
• Consider adding codes for specific symptoms (R21 for rash, L50.0 for urticaria) as secondary diagnoses 5

Important Clinical Considerations

Diagnostic Confirmation

• Patch testing is the gold standard for confirming allergic contact dermatitis to diclofenac, typically performed 3 weeks after resolution of acute symptoms 2
• Testing should include both the commercial gel formulation and diclofenac sodium 1% in petrolatum 2
• Readings at 48 and 72 hours are standard 2

Cross-Reactivity Concerns

• Diclofenac is an acetic acid derivative NSAID, which has higher association with severe cutaneous adverse reactions compared to other NSAID classes 1
• Cross-reactivity within the same chemical class is well-described, though not universal 1
• Consider testing alternative NSAID classes (propionic acids like ibuprofen, or COX-2 inhibitors) if pain management is needed 1

Common Coding Pitfalls to Avoid

• Do not use codes for oral drug reactions (T88.7, adverse effect of drug NOS) for topical contact dermatitis 2
• Do not use photoallergic reaction codes unless sun exposure was documented as a trigger 2
• Avoid using only symptom codes (like R21 for rash) without the underlying allergic etiology code 5
• The combination of a specific ICD-10 code with an external cause (E-code equivalent) significantly improves identification accuracy, with positive predictive values up to 76% 5

Validation Considerations

• ICD-10 code L23.3 has not been specifically validated in large studies, but the analogous ICD-9 code 693.0 (dermatitis due to drug) had an 87% positive predictive value for true allergic drug reactions 5
• T88.6 for anaphylaxis has a positive predictive value of 62.8-77.4% depending on coding specificity 4