Fungal Infections (Mycosis) ICD-10: B49

Fungal / Infectious skin condition

Often searched as: fungal rash on skin, ringworm on body, itchy fungal infection, yeast infection on skin, fungal rash that keeps coming back, skin infection from gym or pool, nail fungus, white patches in mouth yeast…

Clinical urgency level

lowmediumhigh

Systems Affected

skinnailshairmucous membranesinternal organs (in systemic mycoses)

Severity Levels

mild

Superficial infection limited to skin, nails, or mucous membranes in an immunocompetent person — responds well to topical antifungal treatment.

moderate

Persistent, recurrent, or widespread superficial infection, or subcutaneous infection following skin trauma — requires prescription antifungals, systemic in some cases.

severe

Systemic or deep fungal infection (e.g., candidiasis, aspergillosis, cryptococcosis) in immunocompromised individuals — potentially life-threatening, requires urgent hospitalization and IV antifungal therapy.

Red Flags

Fever, chills, or systemic symptoms alongside a skin fungal infection — possible disseminated infection
Rapidly spreading skin infection despite antifungal treatment
Fungal infection in an immunocompromised person (HIV, cancer, transplant, diabetes)
Scalp fungal infection in a child with swelling, pus, or hair loss (kerion — urgent)
White oral patches that bleed when wiped (oral candidiasis in a non-infant) — possible immune deficiency
Any deeply penetrating or rapidly expanding skin lesion in a neutropenic patient

Clinical Presentation

Tinea corporis (ringworm) — circular scaly fungal rash on the arm

Source: Wikimedia Commons (CC BY-SA 3.0 )

Oral candidiasis — white patches on the tongue

Source: Wikimedia Commons (CC BY-SA 3.0 )

When to See a Doctor

See a doctor if a skin fungal infection doesn't improve after 2–4 weeks of over-the-counter antifungal treatment, if it keeps recurring, if nails are involved, or if you have diabetes or a weakened immune system. Any fungal infection with fever or systemic symptoms needs urgent medical evaluation.

Differential Diagnosis

Eczema / contact dermatitis (mimics tinea — 'id reaction' can co-occur)
Psoriasis (can mimic tinea — important distinction before treating)
Seborrheic dermatitis
Bacterial cellulitis (spreading, warm, tender redness)
Pityriasis rosea (herald patch — often mistaken for ringworm)
Erythrasma (bacterial — coral-red fluorescence under Wood's lamp)

Comorbidities

Diabetes mellitus (major risk factor for candidiasis and skin fungal infections)
HIV / AIDS
Organ transplant immunosuppression
Prolonged antibiotic or corticosteroid use
Obesity and hyperhidrosis
Tinea pedis as source of onychomycosis

Prognosis

Superficial fungal infections respond well to antifungal treatment in most immunocompetent people, with cure rates of 70–90% depending on location and agent used. Nail infections are the most resistant and require longer treatment courses. Recurrence is common for all forms if predisposing factors (moisture, immune status, footwear) are not addressed. Systemic mycoses in immunocompromised patients carry significant mortality — up to 40–50% for invasive aspergillosis — underscoring the importance of immune status monitoring.

Detailed Overview

Causes, Symptoms, and When to Take Action Fungal infections, or mycoses, are diseases caused by fungal organisms. They commonly affect the skin, hair, nails, and mucous membranes, but can also involve deeper tissues and organs. How It Looks Texture: On the skin — red, swollen, bumpy, or rash-like lesions; in nails — thickened, cracked, or discolored; in mucous membranes — white patches or coating Color: Varies greatly — red or rash-like on skin; nails can appear yellow, brown, or white; mucosal areas may show pale or white patches Why Does It Appear? Normal flora imbalance: Fungi that normally live on the body can overgrow under certain conditions, such as warm, humid environments Opportunistic infections: A weakened immune system increases susceptibility Superficial vs. deeper infections: Superficial infections affect the skin, nails, or mucous membranes. Systemic infections can involve internal organs and are more serious Should You Be Concerned? Superficial mycoses are generally benign and pose minimal health risk Systemic mycoses can be serious, particularly in immunocompromised individuals Can You Prevent It? Keep skin dry and clean, especially in areas prone to moisture and friction Avoid exposure to communal damp environments without protective measures Maintain good overall health, especially if you have a condition that weakens your immune system 👉 How Piel AI Can Help Piel AI allows you to document and track skin and nail changes over time using images. Although it's not a diagnostic tool, it helps you notice patterns or progression and provides useful information for medical consultations. Summary Mycoses are fungal diseases that range from superficial to systemic infections. Presentation varies by location — skin, nails, or mucous membranes. Weakened immunity increases risk of serious, deep-seated infection. Good hygiene and environmental awareness help reduce superficial infections.

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