ICD-10-CM code B37.2 designates candidiasis of skin and nail — a fungal infection caused by Candida species (most commonly Candida albicans) affecting the integumentary system. This is a billable, valid diagnosis code for fiscal year 2026, effective October 1, 2025, under the ICD-10-CM Official Coding Guidelines published by CMS and the National Center for Health Statistics. Coders apply B37.2 across outpatient clinics, dermatology practices, wound care centers, and inpatient settings where cutaneous or nail-bed candidiasis is the confirmed or treated diagnosis.
What Does ICD-10 Code B37.2 Mean?
B37.2 is a specific, billable ICD-10-CM code that identifies Candida-caused infections confined to the skin and nail structures. It sits within the B37 category (Candidiasis), which itself falls under Chapter 1: Certain Infectious and Parasitic Diseases (A00–B99).
Key attributes at a glance:
- Valid for use: FY2026 (October 1, 2025 – September 30, 2026)
- Billable/Specific: Yes — no additional sub-codes required
- Applicable settings: Outpatient (physician office, dermatology, wound care), inpatient, emergency department
- ICD-9-CM predecessor: 112.3 (Candidiasis of skin and nails)
- Requires “use additional code”: Yes, when applicable — see antifungal resistance (Z16.x) and underlying conditions
What Conditions and Diagnoses Does B37.2 Cover?
B37.2 is the appropriate code when Candida infection is the confirmed etiology affecting the skin surface, skinfolds, or nail apparatus. The ICD-10-CM Tabular includes these specific inclusion terms:
- Candidal intertrigo — Candida infection in body folds (groin, axillae, inframammary, abdominal pannus)
- Candidal paronychia — infection of the nail fold/proximal nail tissue
- Candidal perionyxis — inflammation of the tissue surrounding the nail
- Candidal onychia — infection of the nail plate itself
- Cutaneous candidiasis with satellite pustule pattern
- Erosive candidiasis of intertriginous zones
What Does B37.2 Specifically Exclude?
The ICD-10-CM tabular notes a Type 2 Excludes for B37.2, meaning these conditions are not included but may be coded alongside B37.2 when both are documented:
| Excluded Code | Condition | Coding Note |
|---|---|---|
| L22 | Diaper (napkin) dermatitis | Use L22 + B37.2 together when Candida is confirmed in diaper rash |
| B35.x | Dermatophytosis (tinea) | Separate organism (dermatophyte, not Candida) — do not use B37.2 |
| L30.4 | Erythema intertrigo (non-infectious) | Use B37.2 if Candida is confirmed; L30.4 if etiology is non-infectious |
When Is B37.2 the Right Code to Use?
Selecting B37.2 correctly requires confirming both the site and the causative organism. Follow these criteria in sequence:
- Confirm the site is skin or nail. If the Candida infection involves mucous membranes (oral, vaginal, esophageal), a different B37.x subcode applies (B37.0, B37.3, B37.4).
- Confirm Candida as the causative organism. The provider must document Candida species or clinical findings consistent with candidiasis — not just “fungal infection” generically.
- Verify the condition is not a dermatophyte infection. Tinea pedis, tinea cruris, tinea unguium (onychomycosis due to dermatophytes) map to the B35 category, not B37.2.
- Check for underlying conditions. If the patient is immunocompromised (HIV, organ transplant, long-term corticosteroid use), additional codes are required.
- Review payer policy. Some payers require lab confirmation (KOH prep or fungal culture) on the claim before reimbursing B37.2 as the primary diagnosis.
How Does B37.2 Differ From the Most Commonly Confused Codes?
| Code | Condition | Key Distinction |
|---|---|---|
| B37.2 | Candidiasis of skin and nail | Candida spp. confirmed; skin or nail site |
| B35.1 | Tinea unguium (onychomycosis) | Dermatophyte organism (not Candida); nail only |
| B35.6 | Tinea pedis (athlete’s foot) | Dermatophyte; feet specifically |
| B37.9 | Candidiasis, unspecified | Use only when site cannot be determined from documentation |
| L30.4 | Erythema intertrigo | Non-infectious skinfold irritation; no organism confirmed |
| L22 | Diaper dermatitis | Diaper rash — use with B37.2 when Candida is confirmed |
In practice, coders frequently encounter providers who document “fungal infection” without specifying the organism. When that happens, query the provider before defaulting to B37.9 — a confirmed Candida organism in the clinical notes supports B37.2, which is a more specific and clinically accurate code.
What Documentation Is Required to Support B37.2?
What Must the Provider Document in the Clinical Notes?
Auditors reviewing B37.2 claims will look for these elements in the clinical record:
- Explicit identification of Candida — either by species (e.g., C. albicans, C. tropicalis) or as “candidal” or “candidiasis” in the assessment/plan
- Anatomical site specificity — skin, skinfold location (groin, axilla, inframammary), fingernails, toenails, or nail folds
- Signs and symptoms documented — erythema, satellite pustules, maceration, white nail discoloration, onycholysis
- Risk factors or underlying conditions — diabetes mellitus, immunosuppression, antibiotic use, obesity (supports medical necessity)
- Treatment plan — topical antifungal (clotrimazole, nystatin) or systemic antifungal (fluconazole) prescription; consistent treatment supports the diagnosis
Which Diagnostic or Lab Results Support B37.2?
Lab confirmation is the gold standard for audit defensibility, though clinical diagnosis is acceptable when documented clearly:
- KOH (potassium hydroxide) preparation — demonstrates pseudohyphae or budding yeast; most commonly used office-based test
- Fungal culture — definitively identifies Candida species; preferred for recurrent or treatment-resistant cases
- Histopathology (nail biopsy) — periodic acid-Schiff (PAS) staining confirms fungal elements in nail-bed tissue
- Clinical impression — acceptable when combined with classic presentation (satellite pustules, intertriginous pattern) and documented by a qualified provider
What Is the Documentation Standard for Inpatient vs. Outpatient Settings?
| Setting | Documentation Standard | Sequencing Rule |
|---|---|---|
| Outpatient | Provider’s confirmed diagnosis in the assessment/plan drives code selection | B37.2 as first-listed if it is the reason for the visit |
| Inpatient | Condition established after study may be coded; query if uncertain | Follow UHDDS principal diagnosis rules — sequence the condition most responsible for admission |
| Inpatient (with HIV) | HIV (B20) is always sequenced first per ICD-10-CM guideline I.C.1.a | B37.2 as secondary code when Candida is related to HIV disease |
| Inpatient (with diabetes) | B37.2 may be principal if it drove admission | Add E11.628 or appropriate diabetic complication code as secondary |
How Does B37.2 Affect Medical Billing and Claims?
When B37.2 is the primary diagnosis, billing teams should consider these payer and coverage factors:
- Medical necessity documentation is critical — payers routinely deny antifungal drug claims without documented risk factors, failed OTC treatment, or lab confirmation
- Medicare covers B37.2-related services under standard Part B guidelines; no specific NCD exists for cutaneous candidiasis, but LCDs for dermatology and antifungal therapy may apply
- Medicaid coverage varies by state; check state-specific LCD requirements for antifungal prescriptions
- Coding Clinic guidance (AHA) supports using B37.2 when the provider clearly documents candidal involvement — coders should not assume the code from generic “rash” or “fungal” language alone
What CPT or Procedure Codes Are Commonly Billed With B37.2?
| CPT Code | Description | Typical Pairing Context |
|---|---|---|
| 87220 | KOH preparation for fungi | Ordered during office visit to confirm Candida diagnosis |
| 87102 | Fungal culture, skin | Used for recurrent or resistant cases |
| 11719 | Trimming of nondystrophic nails (≤5) | Nail care visit with concurrent candidal paronychia |
| 99213/99214 | Office/outpatient E/M visit | Primary encounter code when dermatologist or PCP evaluates infection |
| 97597 | Debridement, open wound | Wound care setting when macerated candidal tissue is debrided |
Are There Any Prior Authorization or Coverage Restrictions?
- Oral fluconazole (Diflucan) prescriptions for cutaneous candidiasis often trigger payer step-therapy requirements — documentation of failed topical antifungal therapy may be required before systemic treatment is authorized
- Compounded antifungal preparations frequently require prior authorization with specific payers
- Some payers require lab confirmation (KOH or culture) for repeated B37.2 claims within a short treatment window
- Z16.x resistance codes should be added when antifungal resistance is confirmed — this supports medical necessity for second-line systemic agents
What Coding Errors Should You Avoid With B37.2?
The following errors account for the majority of claim denials and audit findings related to B37.2:
- Using B37.9 (unspecified) when documentation clearly supports B37.2 — failing to capture site specificity is one of the most common undercoding errors in dermatology billing
- Applying B37.2 when the organism is a dermatophyte — tinea infections (B35.x) are caused by dermatophytes, not Candida; lab results or organism documentation should differentiate these
- Missing the “use additional code” instruction — when the patient has HIV (B20) or uncontrolled diabetes, failing to add the secondary code is an audit flag and may affect DRG assignment inpatient
- Coding L22 alone when Candida is confirmed in a diaper rash — B37.2 should be sequenced first, with L22 as secondary, when Candida is the confirmed etiology of the diaper dermatitis
- Billing B37.2 without supporting clinical documentation — generic provider language like “rash, likely fungal” does not support B37.2; the provider must document Candida specifically
- Ignoring sequencing rules in HIV patients — B20 must always be listed before B37.2 per ICD-10-CM Official Coding Guidelines Section I.C.1.a
What Do Auditors Look for When Reviewing Claims With B37.2?
- Evidence that Candida (not another fungal genus) is documented by the treating provider
- Consistency between the diagnosis code, treatment ordered (antifungal specific to candidiasis), and lab results if obtained
- Correct code sequencing when immunocompromising conditions are present
- Absence of a valid clinical reason when B37.9 was used rather than the more specific B37.2
- Documentation of medical necessity for systemic antifungals in outpatient settings
How Does B37.2 Relate to Other ICD-10 Codes?
| Related Code | Relationship | Key Distinction |
|---|---|---|
| B37.0 | Sibling code | Candidal stomatitis (oral thrush) — different site |
| B37.1 | Sibling code | Pulmonary candidiasis — respiratory system involvement |
| B37.3 | Sibling code | Candidiasis of vulva and vagina |
| B37.7 | Sibling code | Candidal sepsis — systemic/bloodstream infection |
| B35.1 | Distinct category | Tinea unguium — dermatophyte onychomycosis |
| B20 | “Code first” trigger | HIV disease — must be listed before B37.2 |
| E11.628 | Common secondary | Type 2 diabetes with other skin complication |
| L22 | Excludes 2 (use together) | Diaper dermatitis — code B37.2 first when Candida confirmed |
| Z16.x | “Use additional” code | Antifungal drug resistance when documented |
What Is the Correct Code Sequencing When B37.2 Appears With Other Diagnoses?
- If the patient has HIV disease (B20): List B20 first, then B37.2 — this is a mandatory rule per ICD-10-CM guidelines regardless of which condition prompted the encounter.
- If the patient has diabetes and candidal skin infection: B37.2 may be principal (outpatient) or secondary (inpatient); add E11.628 or the appropriate diabetes + complication code.
- If diaper candidiasis is confirmed: Sequence B37.2 first, L22 second.
- If antifungal resistance is documented: Add Z16.x as an additional code after the B37.2 primary.
- Inpatient (principal diagnosis): Sequence the condition established after study that is most responsible for the admission — this may or may not be B37.2 depending on clinical context.
Real-World Coding Scenario — How B37.2 Is Applied in Practice
Encounter summary: A 54-year-old woman with Type 2 diabetes mellitus (poorly controlled) presents to her primary care physician with a 3-week history of a bright red, itchy rash in her inframammary skinfold. The provider documents erythematous plaques with characteristic satellite pustules, orders a KOH prep that returns positive for pseudohyphae, and documents “candidal intertrigo, inframammary region.” She is prescribed topical clotrimazole cream and counseled on skinfold hygiene. Her diabetes management is also addressed.
Correct Code Application
- B37.2 — Candidiasis of skin and nail (principal/first-listed diagnosis; Candida confirmed by KOH, site is skin)
- E11.65 — Type 2 diabetes mellitus with hyperglycemia (secondary; documented underlying risk factor)
- CPT 87220 — KOH preparation for fungi (procedure performed during visit)
- CPT 99214 — Office/outpatient E/M, moderate complexity
Common Mistake in This Scenario
- Incorrect code: L30.4 (Erythema intertrigo) or B37.9 (Candidiasis, unspecified)
- Why it fails: L30.4 applies to non-infectious intertrigo — once Candida is confirmed, B37.2 is required. B37.9 is an unspecified code; the KOH result and provider’s explicit “candidal intertrigo” documentation fully support the specificity of B37.2. Using an unspecified or dermatitis code when a confirmed infectious etiology is documented is a diagnosis code specificity failure that creates audit risk and may reduce reimbursement under value-based payment models.
Frequently Asked Questions About ICD-10 Code B37.2
Is ICD-10 Code B37.2 Still Valid in 2026?
B37.2 is a valid, billable ICD-10-CM diagnosis code for fiscal year 2026, with an effective date of October 1, 2025. No changes to the code’s description or validity status were introduced in the FY2026 update. Coders should verify current status annually using the ICD-10-CM Official Coding Guidelines released by CMS each fall.
What Is the Difference Between B37.2 and B37.9?
B37.2 specifies that the candidal infection is located in the skin or nail structures, while B37.9 is an unspecified candidiasis code used only when the site cannot be determined from available documentation. Coders should always query the provider or review the clinical record for site information before defaulting to B37.9 — using unspecified codes when documentation supports specificity is a common audit finding.
Can B37.2 and L22 Be Coded Together?
Yes. The ICD-10-CM tabular lists L22 (diaper dermatitis) as a Type 2 Excludes note under B37.2, meaning both codes may be reported simultaneously when the clinical scenario warrants it. When a candidal infection is confirmed as the cause of diaper rash, sequence B37.2 as the primary code and L22 as the secondary code to capture the full clinical picture.
Does B37.2 Require Lab Confirmation Before It Can Be Coded?
Lab confirmation (KOH prep or fungal culture) is strongly recommended for audit defensibility but is not strictly required for outpatient code assignment. In outpatient settings, coders report the provider’s confirmed diagnosis as documented — if the provider states “candidal intertrigo,” that documentation alone supports B37.2. However, payers may deny antifungal treatment claims without lab evidence, so advising providers on documentation best practices is part of strong revenue cycle compliance.
What CPT Codes Are Most Commonly Billed Alongside B37.2?
The most frequent CPT pairings with B37.2 are 87220 (KOH preparation for fungi), 87102 (fungal culture), and an appropriate E/M service code such as 99213 or 99214. In wound care settings, debridement codes (97597) may also be submitted when macerated candidal tissue is addressed during treatment.
When Must B37.2 Be Listed as a Secondary Diagnosis?
B37.2 must always be listed after B20 (HIV disease) when the candidal skin infection is related to the patient’s HIV status — this is a mandatory sequencing rule per ICD-10-CM Official Coding Guidelines Section I.C.1.a. In other inpatient scenarios, standard UHDDS principal diagnosis rules apply, and B37.2 may be principal or secondary depending on which condition drove the admission.
Key Takeaways
- B37.2 is a specific, billable code — use it when Candida is the confirmed organism and the infection involves skin or nail; do not substitute B37.9 when documentation supports specificity.
- Do not confuse candidiasis with dermatophytosis — tinea infections (B35.x) and Candida infections (B37.2) have different organisms, different treatments, and different ICD-10 codes.
- KOH prep or fungal culture results strengthen audit defensibility, but outpatient code assignment is driven by the provider’s documented diagnosis.
- Sequencing matters — HIV patients require B20 first; candidal diaper rash requires B37.2 before L22; antifungal resistance adds Z16.x as an additional code.
- Common billing errors include using L30.4 for confirmed Candida intertrigo, omitting secondary codes for underlying conditions, and failing to add the resistance code when documented.
- CPT pairings to track: 87220 (KOH), 87102 (culture), 99213/99214 (E/M), and 97597 (debridement in wound care settings).
- For deeper guidance on medical billing documentation requirements and coding audit preparation, consult the CMS ICD-10-CM Resources and the AHA Coding Clinic for the most current official guidance on candidiasis coding.
Sources referenced: CMS ICD-10-CM FY2026 Code Files | WHO ICD-10 Reference | CDC Fungal Disease Surveillance | AHA Coding Clinic, Chapter 1 Infectious Disease guidance