Best Underwear Material for Men — Evidence Review

The Short Answer

1. Scrotal Temperature & Fertility

• Men who mostly wore boxers had 25% higher sperm concentration and 17% higher total sperm count than men wearing tighter underwear.
• They also had 14% lower FSH levels — FSH rises as a compensatory signal when the testes are under thermal stress.
• The mechanism: tight underwear (briefs, boxer-briefs, spandex) elevates scrotal temperature by keeping the testes pressed against the body. The scrotum is designed to hang ~2–4°C below core body temperature for optimal spermatogenesis.
• Fabric type was not isolated in this study (the focus was fit/style), but the mechanism strongly implicates any tight-fitting material — spandex being the worst offender because it stretches to conform and traps heat.

2. Fungal Infection (Tinea Cruris / Jock Itch)

Cotton

• Absorbs moisture but holds it close to the skin once saturated — creates a persistently damp environment if not changed frequently.
• Natural fiber; fewer chemical irritants.
• Best choice for everyday, low-activity wear when changed daily or after sweating.

Spandex / Elastane

• Traps moisture and heat — the worst option for fungal prevention.
• Creates the ideal warm, occluded, humid microclimate that dermatophytes need.
• Widely cited in dermatology as a predisposing factor for tinea cruris and intertrigo.

Polyester / Moisture-Wicking Synthetics

• Wicks sweat away from the skin surface during exercise — reduces surface moisture during activity.
• However, the moisture stays in the fabric and doesn't evaporate as quickly as cotton in low-activity periods.
• Acceptable during sport/exercise; change immediately after — don't wear all day.

Bamboo / Modal

• Gaining popularity: bamboo fabric is naturally antimicrobial, breathable, and moisture-wicking.
• Softer than cotton, better at moisture management.
• Limited formal RCT data, but the properties are well-characterized by textile science.
• A reasonable upgrade over cotton, especially in hot/humid climates.

Merino Wool (blended)

• Naturally antimicrobial (lanolin), excellent temperature regulation, breathable.
• Expensive, but some urologists and dermatologists recommend it for recurrent tinea cruris.

3. Summary Ranking

4. Practical Recommendations

1. Daily wear: Loose-fitting 100% cotton boxers or bamboo/modal underwear — change daily, and after any sweating.
2. Active/sport: Moisture-wicking polyester is fine during exercise — change immediately after; shower and dry thoroughly.
3. Recurrent jock itch: Switch to merino wool or bamboo, keep the groin area dry with talc-free antifungal powder (e.g., miconazole powder), and wear loose boxers.
4. Avoid: Spandex/nylon everyday underwear, staying in wet underwear after exercise, tight-fitting synthetic briefs.
5. Hygiene compounds fabric choice: Any fabric becomes a fungal risk if worn for multiple days or while damp.

5. Research Gaps

Tinea Cruris (Jock Itch): Clinical Guidelines 2025

Causative Organisms

• Primary: Trichophyton rubrum (most common), Epidermophyton floccosum (epidemic outbreaks)
• Secondary: T. mentagrophytes, T. interdigitale
• Important mimic: Candida albicans — moister, more inflammatory, affects the scrotum (unlike true tinea cruris), satellite pustules present
• Emerging concern (2025): Trichophyton indotineae — a newly identified drug-resistant strain first reported in the Indian subcontinent, now spreading globally; does NOT respond reliably to first-line topical or oral antifungals

Diagnosis

Key Differential Diagnosis

• Erythrasma, cutaneous candidiasis, intertrigo
• Inverse (flexural) psoriasis — will not respond to antifungals; misuse of steroid-antifungal combos worsens it
• Seborrheic dermatitis, contact dermatitis, lichen simplex chronicus

Treatment — First-Line

Topical Antifungals (mainstay for localized disease)

• Allylamines and benzylamines are preferred over azoles for shorter treatment duration and sustained mycological cure — Goodman & Gilman's Pharmacological Basis of Therapeutics
• Apply to lesion plus surrounding 2–3 cm of normal skin — applying only to visible lesions causes relapse
• A 2025 systematic review and meta-analysis confirmed Naftifine has superior complete cure rates vs. vehicle (RR = 5.83, 95% CI 3.73–9.10) with a favorable safety profile [PMID 40053133]

⚠️ Avoid steroid-antifungal combination products (e.g., clotrimazole-betamethasone / Lotriderm). These cause temporary symptomatic relief but promote treatment failure, relapse, and resistance — explicitly warned against in Am Fam Physician 2025 guidelines.

Oral Antifungals (for extensive/refractory disease)

• Disease extends beyond groin (lower abdomen, buttocks, perineum)
• No response after 2–4 weeks of topical treatment
• Immunocompromised patient
• Concurrent onychomycosis (nail reservoir driving re-infection)

⚠️ Ketoconazole oral is no longer recommended for superficial infections — risk of severe hepatotoxicity and QT prolongation

Emerging Challenge: Recalcitrant Dermatophytosis (2025)

• Terbinafine resistance is increasingly documented, particularly with T. indotineae
• Itraconazole is now the preferred first-line oral agent for recalcitrant cases (replacing terbinafine)
• However, itraconazole has erratic absorption — super-bioavailable itraconazole formulations are under investigation
• For true dual-resistant cases (terbinafine + itraconazole failure): voriconazole, posaconazole, or ketoconazole used off-label as last resort
• Antifungal susceptibility testing should be performed before treating suspected resistant infection

Prevention Guidelines

1. Control moisture — keep the groin dry; apply talc-free antifungal powder (e.g., miconazole powder) after bathing
2. Wear loose-fitting underwear (boxers, cotton) — tight/occlusive clothing creates the warm, humid microclimate dermatophytes require
3. Treat tinea pedis concurrently — the feet are the most common reservoir for autoinfection. The key tip: put on socks before underwear to avoid transferring fungal spores from feet to groin
4. Change underwear daily, and immediately after exercise
5. Treat household contacts if recurrence is frequent
6. Do not share towels, clothing, or linens
7. Lose weight if obese — skin folds increase occlusion and sweating
8. Apply a barrier zinc-containing cream to prevent skin maceration in recurrence-prone individuals

Key References