Is It Athlete's Foot?
Asymmetry, toe webs and toenails separate fungus from the four things that look like it — and one of the alternatives is urgent.
Part of the Complete Athlete's Foot Guide.
Key fact: Asymmetry is the clue. Fungal infection frequently affects one foot considerably more than the other. Eczema, psoriasis and contact dermatitis on the feet are usually more or less symmetrical — so one scaly foot and one normal one points firmly towards fungus.
The athlete's foot signature
- Asymmetry — one foot noticeably worse than the other
- Starts between the toes, usually the outer webs, in the commonest pattern
- A defined edge where the scaling stops, often running along the side of the foot
- Spreading over weeks rather than flaring and settling
- Toenails involved — thickened or discoloured nails alongside make fungus far more likely
- Itch or stinging, though the scaly moccasin pattern is often silent
- Responds to an antifungal, which eczema and psoriasis do not
Dyshidrotic eczema
Also called pompholyx. Crops of small, deep-seated, intensely itchy blisters on the soles, insteps and the sides of the fingers and toes — and the commonest thing confused with blistering athlete's foot.
| Points to dyshidrotic eczema | Points to fungal infection |
|---|---|
| Both feet, and often the hands too | One foot much worse than the other |
| Blisters look like tapioca, deep in the skin, without surrounding scale | Blisters with a scaly edge, often near an area of peeling |
| Flares and settles in cycles, often with stress or heat | Progresses steadily and spreads outwards |
| Nails normal, or with eczema pitting | Toenails often thickened or discoloured |
| Improves with steroid cream | Worsens, or spreads, with steroid alone |
Confusingly, a fungal infection of the feet can also trigger a blistering reaction on the hands — an id reaction — which clears when the feet are treated. Eczema and dermatitis covers the eczema side.
Contact dermatitis
- Follows the shape of what touched the skin — a strap, the top of a shoe, a stripe where an adhesive sat
- Usually symmetrical, because both feet are in similar shoes
- Spares the toe webs, which is the giveaway, because footwear does not touch them
- Common culprits: rubber accelerators, chromate in leather, dyes, adhesives
- Improves away from the shoes, over a weekend or a holiday
"Spares the toe webs" does most of the work here. Athlete's foot loves the toe webs; a shoe allergy cannot reach them.
Psoriasis
- Thick, well-defined silvery-scaled plaques rather than fine peeling
- Symmetrical, and often on the heels and weight-bearing areas
- Elsewhere too — elbows, knees, scalp, behind the ears, the natal cleft
- Nail changes are different: pitting, and orange-pink "oil drop" patches. Fungal nails crumble and thicken from the free edge
- Chronic and relapsing, rather than steadily spreading
- Does not respond to antifungal cream
Psoriasis and fungal infection can coexist, and psoriatic skin is not protected from fungus — so a psoriatic foot that suddenly develops soggy toe webs may well have both.
Dry skin and juvenile plantar dermatosis
- Simple dry skin — symmetrical, worse in winter, improves with emollient, and spares the toe webs
- Juvenile plantar dermatosis — in children, shiny glazed red skin on the weight-bearing forefoot, with cracking, sparing the toe webs. Related to footwear and sweat rather than fungus
- Athlete's foot is uncommon before puberty, so a scaly-footed child is more likely to have one of these
Erythrasma and bacterial causes
- Erythrasma — a bacterial infection of the toe webs producing brown, finely scaled patches, often less itchy, and typically less soggy than fungal infection. It fluoresces coral-pink under a Wood's lamp and is treated differently
- Pitted keratolysis — small punched-out pits on the sole with a strong smell, from sweaty feet and bacteria, not fungus
- Secondary bacterial infection — fungal toe webs that become very macerated, smelly and weepy often have bacteria on top, and may need more than an antifungal
The one that is urgent
A hot, painful, red, swollen foot or lower leg — particularly with fever or feeling unwell — needs prompt assessment. Cellulitis is a spreading bacterial infection, and cracked skin between the toes from athlete's foot is one of its recognised entry points. This is the specific reason athlete's foot matters in people with diabetes, poor circulation, leg swelling or a previous episode of cellulitis.
How it is confirmed
- Usually on appearance and pattern, particularly with the toe webs involved and one foot worse
- Skin scrapings sent for microscopy and culture, used where the diagnosis is unclear, treatment has failed, or oral treatment is being considered
- Sample before treatment starts, as with nails — antifungal already applied makes the result unreliable
- Nail clippings if the nails are involved, which often settles both questions at once
What to do
- Look between the toes, not just at the sole
- Compare the two feet — asymmetry is the most useful single sign
- Look at the toenails
- Look elsewhere — groin, body, one hand, and for psoriasis on elbows, knees and scalp
- Do not reach for a steroid cream on an undiagnosed scaly rash — see the steroid trap
- If an adequate antifungal course has not worked, reconsider the diagnosis rather than repeating it — treatments compared covers what adequate means
Frequently Asked Questions
How do I know if it is athlete's foot or eczema?
Asymmetry is the most useful sign: fungal infection often affects one foot much more than the other, while eczema is usually symmetrical. Fungal infection typically starts between the toes and spreads steadily with a defined edge; dyshidrotic eczema produces deep itchy blisters on both feet and often the hands, and flares and settles in cycles.
Can athlete's foot affect only one foot?
Yes, and it commonly does. One foot considerably worse than the other points towards fungal infection and away from eczema, psoriasis and contact dermatitis, which are usually more or less symmetrical because both feet are treated the same way.
What else causes peeling skin between the toes?
Erythrasma, a bacterial infection producing brown finely scaled patches, is the main alternative and is treated differently. Contact dermatitis from footwear typically spares the toe webs, because shoes do not touch them, which is a helpful distinguishing feature.
Is athlete's foot common in children?
It is uncommon before puberty. A child with scaly, cracked feet is more likely to have juvenile plantar dermatosis, which produces shiny glazed red skin on the weight-bearing forefoot and spares the toe webs, or simple dry skin.
My antifungal cream is not working. What now?
Check the course was long enough first, at least 4 weeks for clotrimazole and 7 days past clearing for anything. If it was adequate, reconsider the diagnosis: dyshidrotic eczema, contact dermatitis, psoriasis and erythrasma all mimic athlete's foot and none responds to antifungals.
References
- NHS. Athlete's foot. nhs.uk
- NHS. Ringworm and other fungal infections. nhs.uk
- National Institute for Health and Care Excellence. Clinical Knowledge Summary: Fungal skin infection — foot. cks.nice.org.uk
- Nottinghamshire Area Prescribing Committee. Dermatophyte infection of the skin. nottsapc.nhs.uk
- DermNet. Tinea corporis and tinea incognito. dermnetnz.org
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. A steroid cream applied to a fungal rash makes it spread while looking better, so a rash that is not clearly diagnosed should be assessed rather than treated with whatever is in the cupboard. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.