What are the causes and treatments of a rash on the penis?

Penile Rash: Causes and Treatment

A penile rash requires immediate evaluation to distinguish between common infectious causes (genital herpes, candidal balanitis), sexually transmitted infections, and life-threatening conditions like Fournier gangrene, with treatment directed at the specific underlying etiology.

Diagnostic Approach

Initial Assessment

• Look for vesicular or ulcerative lesions on the penis, buttocks, or perineum, which suggest genital herpes and require laboratory confirmation with viral culture or nucleic acid amplification testing 1
• Examine for erythematous patches with pruritus or irritation on the glans penis, which indicates candidal balanitis—the most frequent mycotic infection of the penis 1, 2
• Assess for systemic signs including fever, tachycardia, and severe pain, which may indicate necrotizing infections like Fournier gangrene requiring emergency surgical intervention 1
• Obtain sexual history to determine risk for sexually transmitted infections, as HSV is the most common cause of sexually acquired genital ulceration 1

Critical Red Flags

• Rapidly progressive skin necrosis with discrete areas of necrosis in the perineum extending to the penis suggests Fournier gangrene, which requires immediate surgical debridement and broad-spectrum antibiotics covering mixed aerobic and anaerobic flora 1
• Intense pain, fever, or signs of systemic toxicity warrant immediate hospitalization and specialist consultation 3, 4

Common Etiologies and Treatment

Genital Herpes (HSV-1 or HSV-2)

• Clinical presentation: Vesicular rash that progresses to shallow ulcers or erosions, typically lasting less than 10 days 1
• Diagnosis: Laboratory confirmation is essential as clinical diagnosis alone leads to both false positives and false negatives; collect vesicle fluid with sterile swab for viral culture or nucleic acid amplification testing 1
• Treatment: Antiviral therapy (specific regimens not detailed in provided guidelines, but diagnosis confirmation is the priority) 1

Candidal Balanitis

• Clinical presentation: Erythematous areas on the glans penis with pruritus or irritation 1
• Treatment: Topical antifungal agents applied to relieve symptoms; systemic treatment is recommended for widespread infections 1, 2
• Partner consideration: Male partners of women with vulvovaginal candidiasis may develop balanitis and benefit from topical antifungal treatment 1

Contact Dermatitis/Irritant Reactions

• Treatment: Hydrocortisone topical cream applied to affected area not more than 3 to 4 times daily for adults and children 2 years and older 5
• Application technique: When practical, clean the affected area with mild soap and warm water, rinse thoroughly, and gently dry before applying 5

Fixed Drug Eruption

• Clinical presentation: Oval-circular erythematous patch with itching and burning pain that appears after drug exposure (commonly trimethoprim-sulfamethoxazole) 6
• Management: Immediate discontinuation of the offending drug and topical corticosteroids twice daily to prevent generalized reactions 6
• Education: Patient must be counseled to avoid the causative medication permanently 6

Cellulitis of the Penis

• Clinical presentation: Local and systemic signs that progress rapidly, most often in young men following sexual intercourse 7
• Causative organisms: Group B hemolytic streptococci are usual pathogens; less virulent organisms in immunocompromised patients 7
• Treatment: Appropriate antibiotics resolve local and systemic symptoms and avoid complications 7

When to Consider STI-Related Causes

Urethritis/Epididymitis with Penile Symptoms

• For men ≤35 years: Consider N. gonorrhoeae and C. trachomatis; treat with ceftriaxone 250 mg IM single dose PLUS doxycycline 100 mg orally twice daily for 10 days 3, 4
• For men >35 years: Consider enteric organisms (E. coli); treat with ofloxacin 300 mg orally twice daily for 10 days OR levofloxacin 500 mg orally once daily for 10 days 3, 8, 4
• Diagnostic testing: Obtain Gram-stained smear of urethral exudate, culture or nucleic acid amplification test for N. gonorrhoeae and C. trachomatis, and consider syphilis serology and HIV testing 3, 4

Common Pitfalls to Avoid

• Do not rely on clinical diagnosis alone for genital ulceration—always obtain laboratory confirmation, as HSV and Treponema pallidum can coexist in the same lesion 1
• Do not delay treatment for suspected Fournier gangrene—this necrotizing infection requires immediate surgical debridement and can progress from innocuous lesions to life-threatening infection within 24 hours 1
• Do not overlook systemic diseases—penile rashes can be the first presentation of conditions like Henoch-Schönlein purpura or represent penile involvement in systemic mycosis in immunocompromised patients 2, 9
• Do not treat empirically without considering the patient's age and risk factors—treatment algorithms differ significantly for patients above and below 35 years of age 3, 8, 4