ConditionSkin, hair & nails
Erythrasma
Erythrasma is a mild, superficial skin infection caused by the bacterium Corynebacterium minutissimum. It produces smooth, pink to reddish-brown patches in warm skin folds such as the groin, armpits and between the toes. It is often mistaken for jock itch or a yeast rash, but it is bacterial, so antifungal creams that lack antibacterial activity may not clear it. Under a Wood's lamp it glows coral red, and it responds well to topical or oral antibiotics.
Also called: Corynebacterium minutissimum infection, interdigital erythrasma
At a glance
- What it is
- A superficial bacterial infection of skin folds caused by Corynebacterium minutissimum.
- Where
- Groin, inner thighs, armpits, between the toes, under the breasts and around the anus.
- Looks like
- Well-defined pink, red or brown patches with fine scale, usually little or no itch.
- Diagnosis
- Coral-red glow under a Wood's lamp (ultraviolet light).
- Treatment
- Topical antibiotics (such as erythromycin or clindamycin), fusidic acid where available, or a short course of oral antibiotics. Recurrences are common.
When to get help
See a doctor within a day or two
- A spreading, hot, painful red area with fever, which suggests cellulitis rather than erythrasma
- Cracked, oozing skin between the toes with redness spreading up the foot, especially if you have diabetes
Book a routine appointment
- A brown or pink rash in the groin or armpit that has not improved after 2 weeks of antifungal cream
- Patches that keep coming back after treatment
- Any new rash in skin folds if you have diabetes or a weakened immune system
Usually safe to manage at home
- Mild, stable patches in skin folds while you keep the area clean and dry, and arrange an appointment
What erythrasma is
Corynebacterium minutissimum is a bacterium that normally lives harmlessly on human skin. In warm, moist, rubbed areas it can overgrow in the outer dead layer of skin (the stratum corneum) and cause a rash. It does not invade deeper and is not dangerous by itself, but it can be stubborn and cosmetically bothersome.
The bacteria produce a pigment called coproporphyrin III. This is why the rash glows coral pink or red under ultraviolet light, a feature that sets it apart from most other rashes.
Symptoms and where it appears
| Type | Where | What you notice |
|---|---|---|
| Interdigital (toe web) | Between the toes, most often the 4th and 5th | White, soft, peeling or cracked skin; the most common form, often mistaken for athlete's foot |
| Intertriginous | Groin and inner thighs, armpits, under breasts, between buttocks | Sharply outlined pink-red patches that turn brown, with fine wrinkled scale |
| Disseminated | Trunk and limbs | Larger scaly patches, rare, mostly in people with diabetes |
Most people have mild or no itching. Some have a burning feeling or mild irritation when sweating.
Who gets erythrasma
- People with diabetes, which is the strongest link. Widespread or repeated erythrasma is a reason to check blood sugar.
- Obesity and deep skin folds.
- Hot, humid climates and heavy sweating.
- Older age.
- Poor hygiene or living in crowded conditions.
- A weakened immune system.
Erythrasma vs jock itch and other fold rashes
| Feature | Erythrasma | Jock itch (tinea cruris) | Candida (yeast) | Inverse psoriasis |
|---|---|---|---|---|
| Cause | Bacteria | Fungus | Yeast | Immune skin disease |
| Edge | Uniform color, no raised border | Raised, scaly, active edge with clearer center | Bright red with small "satellite" spots | Sharp, shiny red, little scale |
| Itch | Mild or none | Often intense | Itchy and sore | Variable |
| Scrotum | Usually spared | Usually spared | Often involved | Can be involved |
| Wood's lamp | Coral red glow | No glow | No glow | No glow |
Erythrasma and fungal infections can occur together, especially between the toes. That is one reason a rash may only partly respond to one treatment. Another common fold rash is intertrigo, simple inflammation from friction and moisture.
How erythrasma is diagnosed
- Wood's lamp examination: a handheld ultraviolet lamp in a darkened room shows the coral-red fluorescence. Washing the area within the previous day or so can wash away the pigment and give a false negative.
- Skin scraping: examined under a microscope to look for fungus, which helps rule out tinea or yeast. A special stain (Gram stain) can show the rod-shaped bacteria.
- Blood sugar test: if erythrasma is extensive or recurrent.
Treatment for erythrasma
Topical treatment (first choice for limited patches)
- Erythromycin or clindamycin cream, gel or solution, applied twice daily, usually for 1 to 2 weeks.
- Fusidic acid cream (outside the US).
- Azole creams such as miconazole or clotrimazole have some antibacterial effect and also cover a fungal infection, which is useful when both are present.
- Benzoyl peroxide wash can help clear and prevent recurrence.
Oral antibiotics
For widespread or stubborn erythrasma, a doctor may prescribe a single dose or short course of an oral antibiotic such as clarithromycin or erythromycin.
Light treatment
Red light photodynamic therapy can activate the bacteria's own porphyrin pigment, and has been used for resistant cases.
The color change may take several weeks to fade completely even after the infection has cleared.
Preventing erythrasma from coming back
Recurrence is common, especially with diabetes or obesity.
- Wash with soap or an antibacterial wash, and dry skin folds thoroughly.
- Wear loose, breathable cotton clothing, and change out of damp clothes or socks promptly.
- Use an absorbent powder in skin folds and between the toes.
- Keep blood sugar well controlled.
- Lose weight if skin folds are a problem.
- Some doctors suggest using an antibacterial wash once or twice a week as maintenance.
Frequently asked questions
What does erythrasma look like?
It looks like smooth, clearly outlined pink to reddish-brown patches with very fine scale, usually in the groin, armpits or between the toes. Unlike ringworm or jock itch, it has no raised, scaly ring at the edge. It often causes little itching, so it may go unnoticed for months.
Is erythrasma a fungal infection?
No. Erythrasma is caused by bacteria, Corynebacterium minutissimum. It is often mistaken for a fungal rash like jock itch, and the two can coexist. Pure antifungal creams may not clear it, although azole creams have some antibacterial action and can help.
How do you get rid of erythrasma fast?
A topical antibiotic such as erythromycin or clindamycin applied twice daily usually clears limited erythrasma within 1 to 2 weeks. For larger areas, a doctor may prescribe a short course of oral antibiotics. Keeping the skin dry and washing with an antibacterial soap speeds healing and prevents recurrence.
Is erythrasma contagious?
It is only mildly contagious. The bacteria normally live on everyone's skin, and erythrasma develops mainly because of warmth, moisture and personal risk factors such as diabetes, rather than catching it from someone. Sharing towels may contribute, so avoid it during infection.
Why does erythrasma glow under a Wood's lamp?
The bacteria make a pigment called coproporphyrin III, which glows coral red under ultraviolet light. This makes a Wood's lamp a quick, painless way to diagnose erythrasma and to tell it apart from fungal infections, which do not glow this color.
Sources
This guide was written from current patient and clinical guidance, including:
- DermNet: Erythrasma
- American Osteopathic College of Dermatology: Erythrasma
- Merck Manual Professional Version: Erythrasma
- StatPearls (NCBI Bookshelf): Erythrasma
- Primary Care Dermatology Society (UK): Erythrasma