ICD-10 Code L74.1 – Miliaria crystallina (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code L74.1 – Miliaria crystallina
What it is
Miliaria crystallina is a superficial sweat-duct blockage that causes tiny, clear blisters on the skin. It is a mild form of heat rash and usually resolves quickly when sweating and heat exposure decrease.
Clinical signs
Look for small, fragile, noninflamed vesicles that may appear in clusters, often on the trunk or areas exposed to heat. Clinical features vary; refer to documentation.
When to use this code
Use L74.1 when the provider documents miliaria crystallina, heat rash, or sweat duct obstruction with clear vesicles. Code it only when the diagnosis is confirmed in the record, not for nonspecific itching or rash without a stated type.
Do not use for
Do not use this code for other miliaria forms, such as rubra or profunda, unless documentation specifically identifies crystallina. Check documentation if the rash is described differently or the diagnosis is uncertain.
Coding tip
Assign L74.1 only when the note clearly names miliaria crystallina; otherwise, query for the exact rash type.