Groin Rash: Causes and How to Treat It

Why the groin gets rashes

The groin is warm, moist and covered, and skin rubs against skin with every step. Sweat softens the skin, friction breaks down its barrier, and fungi, yeast and bacteria that normally live on the skin can overgrow. Tight clothing, sport, hot weather, obesity, diabetes and antibiotics all make this more likely. That is why most groin rashes are infections or irritation rather than an allergy.

Common causes of a groin rash

Jock itch (tinea cruris)

Jock itch is a fungal infection caused by the same dermatophyte fungi as athlete's foot. It is much more common in men.

• A red or brown, itchy patch that spreads outward from the crease onto the inner thigh
• A sharper, raised, scaly edge with a clearer center, like a half-ring
• Usually spares the scrotum and penis
• Often appears alongside athlete's foot, which can reinfect the groin

Yeast infection (candidal intertrigo)

Candida yeast causes a bright, beefy red, moist rash in the folds.

• Small red spots or pustules scattered just outside the main patch ("satellite lesions")
• Often involves the scrotum in men and the vulva in women
• More common with diabetes, obesity, recent antibiotics, steroid use and in babies in diapers
• Can occur with a vaginal yeast infection

Intertrigo from friction and sweat

Intertrigo is irritation where two skin surfaces rub together. The fold looks red, raw and sometimes cracked, with a mirror-image pattern on both sides. It stings more than it itches. It often becomes infected with yeast or bacteria if left moist.

Contact dermatitis

Contact dermatitis is a reaction to something touching the skin: new laundry detergent, fabric softener, scented wipes, condoms or lubricants, hair-removal creams, or the antifungal or antibiotic cream used to treat the rash. It causes itchy redness, sometimes with tiny blisters, in the exact area of contact.

Erythrasma

Erythrasma is a mild bacterial infection that makes a flat, brown or pinkish-brown patch with fine scale and a smooth edge. It itches only a little and does not respond to antifungals. Under a Wood's lamp (ultraviolet light) it glows coral-red, which is how doctors confirm it.

Heat rash and folliculitis

Heat rash produces tiny, itchy or prickly bumps after sweating. Folliculitis is infection of hair follicles, often after shaving or waxing, and causes small pus-filled spots centered on hairs.

Less common but important causes

• Inverse psoriasis: smooth, shiny, sharply outlined red patches in the folds, without the thick scale of psoriasis elsewhere. Look for psoriasis on the scalp, elbows or nails.
• Seborrheic dermatitis: greasy, pink, mildly scaly patches, often with dandruff.
• Hidradenitis suppurativa: painful, deep lumps and boils that recur in the groin and armpits and leave scars and draining tunnels. It is often mistaken for repeated boils.
• Scabies: intensely itchy small bumps, worse at night, on the genitals, waist and between the fingers.
• Pubic lice: itching in the pubic hair, with visible lice or eggs on the hairs.

Sexually transmitted infections that cause a groin rash

STIs can look like an ordinary rash at first. Get tested if you notice:

• Genital herpes: clusters of small painful blisters that burst into shallow sores, often with tingling beforehand. See genital herpes.
• Syphilis: a painless sore (chancre), then weeks later a non-itchy rash that may include the palms and soles.
• Genital warts: soft, flesh-colored bumps, sometimes cauliflower-like.
• Molluscum contagiosum: small, firm, pearly bumps with a central dimple.

How to tell groin rashes apart

Groin rash in men and women

In men, jock itch is the leading cause, especially in athletes and in hot weather. A rash on the scrotum is more likely to be candida, eczema or psoriasis than jock itch. Itching of the scrotum alone, without a rash, is often from dry skin or irritants.

In women, candida is more common than jock itch and may accompany a vaginal yeast infection with discharge and vulvar itching. Shaving and waxing often trigger folliculitis. Lichen sclerosus, which causes white, thin, itchy skin around the vulva and anus, can be mistaken for a groin rash.

In babies, a groin rash is usually diaper dermatitis or candida.

How a doctor diagnoses a groin rash

Most groin rashes are diagnosed by looking at them. A doctor may also:

• scrape scale onto a slide (KOH test) to see fungus or yeast under a microscope
• use a Wood's lamp to check for erythrasma
• swab blisters or sores for herpes, or take blood for syphilis and HIV
• check blood sugar if yeast infections keep recurring
• take a small skin biopsy if the rash does not respond to treatment

Groin rash treatment

Self-care for any groin rash

• Wash gently with water and a fragrance-free cleanser, then dry thoroughly. Pat, do not rub. A hair dryer on a cool setting helps.
• Wear loose cotton underwear and change out of sweaty clothes promptly.
• Avoid scented products, wipes and talc on the area.
• Lose weight if folds are deep, and keep diabetes well controlled.

Over-the-counter treatments

• Antifungal creams (terbinafine, clotrimazole, miconazole) for jock itch and yeast. Apply 2 cm beyond the edge of the rash, and continue for 1 to 2 weeks after it clears. Treat athlete's foot at the same time.
• Hydrocortisone 1% cream for a short time can ease irritant or allergic dermatitis. Do not use a steroid cream alone on a fungal rash: it can make jock itch spread and change its appearance (tinea incognito).
• Barrier creams with zinc oxide protect raw skin from friction and moisture.

Prescription treatments

Doctors may prescribe oral antifungal tablets for extensive fungal infection, antibiotics for erythrasma or cellulitis, stronger anti-inflammatory creams for psoriasis, antiviral medicine for herpes, or treatments for scabies and lice that also cover close contacts.

Preventing groin rashes

• Dry the groin fully after showering and sport.
• Put socks on before underwear if you have athlete's foot, so the fungus is not carried up.
• Do not share towels.
• Wash workout clothes after every use.
• Use an anti-chafing balm or moisture-wicking shorts for running.

Frequently asked questions

What is the most common cause of a groin rash?

Jock itch (tinea cruris), a fungal infection, is the most common cause in men, especially athletes. In women, babies and people with diabetes, candida yeast is more common. Chafing, contact dermatitis and erythrasma are also frequent causes.

How can I tell if my groin rash is fungal?

A fungal rash typically has a raised, scaly, red edge that spreads outward with clearer skin in the middle, and it itches. Yeast rashes are bright red and moist with small spots beyond the edge. A doctor can confirm with a quick skin scraping under a microscope.

Why is my inner thigh rash not going away?

Common reasons are stopping antifungal cream too early, using a steroid cream that feeds the fungus, untreated athlete's foot, or a rash that is not fungal at all, such as erythrasma, psoriasis or contact dermatitis. See a doctor if it has not improved after 2 weeks of treatment.

Can a groin rash be an STI?

Yes. Clusters of painful blisters suggest herpes, a painless sore may be syphilis, and soft bumps can be genital warts or molluscum. These need testing. Most itchy, scaly, ring-shaped rashes in the folds are not sexually transmitted.

Should I put hydrocortisone on a groin rash?

Only for a rash you are confident is irritation or eczema, and only for a few days. On a fungal rash, hydrocortisone alone can make it spread and harder to diagnose. If you are unsure, use an antifungal cream first or ask a pharmacist or doctor.