What causes black substances attached to hair on the scrotum, and what should be done about it?

Black substances attached to scrotal hair are commonly caused by a mixture of sebum and sweat with dirt, blood crusts after shaving, folliculitis, fungal infections, or lice excrement. Patients may choose appropriate cleaning, medical treatment, or surgical intervention based on specific symptoms. Detailed analysis is as follows:

1. Sebum and sweat mixed with dirt

The scrotum contains dense sebaceous glands. Secretions mix with sweat and dead skin, oxidize, turn black, and adhere to hair roots. Clean daily with warm water, wear breathable cotton underwear, and avoid prolonged sitting in damp environments.

2. Blood crusts after shaving

Minor cuts from shaving cause tiny wounds; oozing blood oxidizes into black flakes. Stop shaving temporarily, apply petroleum jelly for moisturization, avoid scrubbing with hot water within 48 hours, and allow the scab to fall off naturally.

3. Folliculitis

Infection of hair follicles by *Staphylococcus aureus* leads to redness, swelling, and pustules, which leave black crusts upon drying. Topical treatments include mupirocin ointment, fusidic acid cream, or clindamycin phosphate gel, applied twice daily for one week.

4. Tinea cruris (jock itch)

Infection of the groin area by *Trichophyton rubrum* causes raised borders with scaling; scratching results in pigmentation appearing as black spots. Use topical terbinafine cream, ketoconazole cream, or bifonazole spray consistently for four weeks, and keep the area dry.

5. Pediculosis pubis (crabs)

Louse excrement appears as rust-colored granules tightly adhering to hair shafts, causing intense itching that worsens at night. After shaving off pubic hair, apply lindane lotion, permethrin cream, or malathion lotion. Wash clothing and bed linens in hot water at 60°C, and treat sexual partners simultaneously.

Routine care includes daily washing with warm water, avoiding shared towels, and cleaning before and after sexual activity. Disinfect shaving tools before and after use to reduce friction. Seek prompt evaluation at a dermatology clinic if black particles continue to increase or are accompanied by ulceration and discharge.