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Chapter 12: Diseases of the skin and subcutaneous tissue (L00–L99)

Skin and tissue conditions: eczema and dermatitis, psoriasis, acne, skin infections such as cellulitis, pressure ulcers, urticaria (hives), and hair and nail disorders.

Chapter 12 spans codes L00–L99 in the FY2027 ICD-10-CM tabular list. This guide explains 29 of its most common codes — select a code for its official description, a plain-English explanation and a note on when the code is used.

ICD-10 Chapter 12: Skin & Subcutaneous Tissue — illustrative image

Codes in this chapter

CodeOfficial descriptionIn plain words
L01.00Impetigo, unspecifiedImpetigo is a contagious superficial skin infection, usually with honey-coloured crusts, common in children.
L02.91Cutaneous abscess, unspecifiedA cutaneous abscess is a pocket of pus under the skin causing a painful, swollen lump; the site is not specified here.
L03.115Cellulitis of right lower limbCellulitis of the right lower leg: a spreading bacterial skin infection causing redness, warmth, swelling and pain.
L03.116Cellulitis of left lower limbCellulitis of the left lower leg: a spreading bacterial skin infection causing redness, warmth, swelling and pain.
L03.90Cellulitis, unspecifiedCellulitis is a bacterial infection of the skin and the tissues beneath it, causing spreading redness, pain and swelling.
L20.9Atopic dermatitis, unspecifiedAtopic dermatitis (eczema) is a chronic itchy, inflamed skin condition linked to allergy and asthma, often starting in childhood.
L21.9Seborrheic dermatitis, unspecifiedSeborrhoeic dermatitis causes scaly, flaky patches on the scalp (dandruff), face and chest, linked to skin yeasts.
L25.9Unspecified contact dermatitis, unspecified causeContact dermatitis is a skin reaction to something touching the skin; neither the type nor the cause is specified here.
L29.9Pruritus, unspecifiedPruritus means itching of the skin, recorded here without a specified cause or rash type.
L30.9Dermatitis, unspecifiedDermatitis means inflammation of the skin with itching, redness and scaling; the type is not specified here.
L40.0Psoriasis vulgarisPsoriasis vulgaris (plaque psoriasis) is the commonest form of psoriasis: raised, red, scaly plaques on elbows, knees and scalp.
L40.9Psoriasis, unspecifiedPsoriasis is a chronic immune-mediated skin condition causing rapid skin-cell turnover and scaly plaques.
L42Pityriasis roseaPityriasis rosea is a self-limiting rash of oval pink patches, often starting with a single larger 'herald' patch.
L43.9Lichen planus, unspecifiedLichen planus is an itchy, purple, flat-topped spotty rash affecting skin, mouth or nails; cause not specified here.
L50.9Urticaria, unspecifiedUrticaria (hives) is an itchy, raised, blotchy rash caused by histamine release in the skin, often allergic.
L57.0Actinic keratosisActinic keratosis is a rough, scaly patch on sun-damaged skin that is precancerous and can occasionally become squamous cell carcinoma.
L60.0Ingrowing nailAn ingrowing nail is when the edge of a toenail grows into the surrounding skin, causing pain and sometimes infection.
L65.9Nonscarring hair loss, unspecifiedNonscarring hair loss means thinning or shedding of hair in which the follicles survive and regrowth is possible.
L70.0Acne vulgarisAcne vulgaris is the common form of acne: blocked pores, spots and inflammation of the face, chest and back, mainly in teenagers.
L71.9Rosacea, unspecifiedRosacea is a chronic facial skin condition causing flushing, persistent redness, spots and visible blood vessels.
L72.0Epidermal cystAn epidermal (epidermoid) cyst is a benign, slow-growing lump under the skin filled with keratin.
L73.2Hidradenitis suppurativaHidradenitis suppurativa is a chronic condition of painful, recurring boils and tunnels in skin folds such as the armpits and groin.
L82.1Other seborrheic keratosisSeborrhoeic keratosis is a common benign, warty, 'stuck-on' skin growth of older adults.
L84Corns and callositiesCorns and callosities are areas of thickened hard skin caused by repeated pressure or friction, usually on the feet.
L85.3Xerosis cutisXerosis cutis is abnormally dry skin, common in older adults and in cold weather, causing roughness and itching.
L89.90Pressure ulcer of unspecified site, unspecified stageA pressure ulcer (bedsore) is skin damage from prolonged pressure, here with site and depth not specified.
L91.8Other hypertrophic disorders of the skinOther hypertrophic skin disorders include skin tags: small, soft, benign flaps of skin in folds such as the neck and armpits.
L97.909Non-pressure chronic ulcer of unspecified part of unspecified lower leg with unspecified severityA non-pressure chronic ulcer of the leg: a long-standing open sore not caused by pressure, with site and depth unspecified.
L98.9Disorder of the skin and subcutaneous tissue, unspecifiedA disorder of the skin or tissue beneath it recorded without further detail.

This guide explains ICD-10-CM codes in plain language for patients, students and other readers. It is educational information only — not coding, billing or medical advice. The code recorded for any real encounter is assigned from the full clinical documentation by the treating team and qualified coders, and only they can decide which code fits a specific case.

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