Reviewed by Evan Lewis, PhD. Last updated August 2026.
A plantar wart is a viral infection with black dots that breaks up your skin lines and hurts when squeezed from the sides. A corn is a small deep plug of pressure-thickened skin that hurts when pressed straight down. A callus is broad, even thickening that usually doesn't hurt at all. Four questions will separate them.
The one-line version of each
Plantar wart. Human papillomavirus infecting the top layers of skin. Contagious. Rough and grainy, usually with pinpoint black dots, and the ridge pattern of your sole stops at its edge.
Corn. Skin thickening in a small concentrated spot because a bone underneath and a shoe on top keep pressing it. Not contagious. Has a hard translucent core that hurts when you stand on it.
Callus. The same pressure response spread over a wider area, with soft edges and no core. Usually painless. It's protection, not a problem, unless it cracks.
The three-way comparison
| Plantar wart | Corn | Callus | |
|---|---|---|---|
| Cause | HPV infection | Concentrated pressure over a bony point | Repeated pressure over a wider area |
| Black dots | Usually visible | None | None |
| Skin lines | Stop at the edge | Run over the top | Run across it |
| Centre | Rough and grainy | Hard, translucent, waxy plug | No distinct centre |
| Edges | Sharply defined, often a raised rim | Sharply defined, small | Soft and fading into normal skin |
| Size | Millimetres to a couple of centimetres | Small and deep | Broad and shallow |
| Worst pain | Squeezed from the sides | Pressed straight down | Usually painless |
| Where | Anywhere on the sole or toes | Pressure points only | Weight-bearing areas, heel and ball |
| Contagious | Yes | No | No |
| Spreads | Yes, can seed nearby skin | No | No |
| Bleeds when filed | Pinpoint bleeding from the capillaries | No, just more hard skin | No, just more hard skin |
Question 1: can you see tiny black dots?
Warts build their own blood supply. Those little vessels get pinched, they clot, and they show through the surface as pinpoint black or dark red dots. Neither a corn nor a callus has a blood supply of its own, so neither has dots.
A 2023 dermoscopy study of 70 patients found black or red dots present in 100% of warts and absent in every corn and callus examined. If you can see dots, you can more or less stop here.
File the surface back gently first if there's a layer of dead skin over the top, because that hides them.
Question 2: do your skin lines carry on across it?
Your soles have ridge patterns, the same as fingerprints. This is the check almost nobody knows, and it's the most useful thing on this page.
A corn and a callus are your own skin getting thicker, so the ridge pattern rides straight over them. A wart replaces the skin, so the pattern stops dead at its border and starts again on the other side.
The same 2023 study found skin lines intact in every callus, and interrupted in every wart. Corns sat mostly with the calluses, with lines intact in about 86% of cases.
Good light, get close, and trace one line into the lump with your eye.
Question 3: is there a hard centre, and does it hurt most pressed straight down?
That combination is a corn.
In the same study, a translucent central core showed in 92.85% of unpared corns and 100% of pared ones, while calluses showed an even opacity with no core at all. That core is the difference between a corn and a callus in one feature.
The pain direction backs it up. DermNet states that tenderness is maximal with lateral pressure for a plantar wart, whereas a corn or callus is more tender with direct pressure. Squeeze it sideways, then press it down, and see which makes you flinch. The pinch test walks through it step by step.
Question 4: is it wide, even and mostly painless?
Then it's a callus, and it's doing its job. Calluses are your skin protecting a weight-bearing area. Runners have them. Nurses have them. So does anyone who stands on concrete for a living.
A callus only becomes a problem when it gets thick enough to crack, or when it's hiding something. Warts under callus are one of the most common reasons people get this wrong for months.
Where each one shows up
Location on its own is decent evidence.
Corns follow bone. Outside of the little toe, top of a bent toe, between the fourth and fifth toes, over a prominent metatarsal head under the ball. If your lump is somewhere no shoe presses, a corn is unlikely.
Calluses follow weight. The heel rim, the ball of the foot, sometimes the side of the big toe.
Warts follow nothing in particular. The arch, the instep, the side of the foot, between toes, in a scattered cluster. They go wherever the virus got in, which is usually through softened or slightly broken skin on a damp shared floor.
What each one responds to
Corn. The pressure. Take it away with a wider shoe, a rounder toe box, a lower heel, softer insoles, and it stops rebuilding. A chiropodist or podiatrist can pare a painful one down in minutes. It returns if the pressure returns, and no bottle changes that, ours included.
Callus. Time and moisture. The NHS advice is to soak in warm water, file gently with a pumice stone, moisturise regularly, and wear thick cushioned socks and wide shoes with a low heel. Don't cut it. A callus that's not cracking or hurting is fine left alone.
Wart. Largely your own immune system, over time. DermNet reports that in children around 50% of warts clear within six months and 90% within two years, with adults generally slower. Anything else you do sits alongside that. If you want the technical reading on elemental iodine in this area, our research lead's white paper on wart and fungal nail management covers it.
The one thing worth saying about all three: the skin around them takes the damage. Skin that's split, macerated or burnt by a misapplied medicated pad is how a small problem becomes a long one. Looking after that skin is the part that's genuinely in your hands, and it's the job Sole Shield was built for. Two ingredients, iodine and pure water, on feet and into shoes. No alcohol on skin that's already dry, no sting, no staining.
When to skip all four questions
- It's bleeding, weeping or open
- It's changing shape, size or colour
- It hurts enough to change how you walk
- There are several and the number is going up
- You have diabetes, poor circulation, or reduced feeling in your feet
The NHS is unambiguous on the last one: if you have diabetes, circulation problems, a weakened immune system, or you're older, don't treat corns and calluses yourself. And don't cut any of these out with clippers or a blade, whatever they turn out to be.
Common questions
How do you tell a plantar wart from a corn or a callus?
Look for black dots, then follow your skin lines. Warts show pinpoint black dots and the skin line pattern stops at their edge. Corns and calluses have no dots and the lines run straight over them. Corns are small with a hard core and hurt on downward pressure. Calluses are broad, even and usually painless.
Can a callus turn into a plantar wart?
No. A callus is your own thickened skin and a wart is a viral infection, so one does not become the other. What happens often is that a wart forms in a weight-bearing area and callus builds over the top of it, which hides the wart and makes the whole thing look like a plain callus for months.
Does a plantar wart bleed when you file it?
Yes, typically as pinpoint bleeding from the small capillaries running up into it. A corn or a callus just reveals more hard skin. That difference is one of the signs clinicians use, though it is not a reason to file aggressively at home, which risks breaking the skin and spreading a wart further.
Which one is contagious?
Only the wart. It is caused by human papillomavirus and can spread to other spots on your own foot and to other people, usually through damp shared floors like changing rooms and pool surrounds. Corns and calluses are mechanical responses to pressure and cannot be passed on.
Is a corn just a small callus?
Close, but not identical. Both are the skin thickening under pressure. A callus spreads the thickening over a wide area with soft edges and no core, while a corn concentrates it into a small deep plug with a hard translucent centre, which is what makes corns painful and calluses usually not.
What happens if I treat a wart as a corn by mistake?
At best nothing. At worst, medicated corn plasters act on the healthy skin around the lesion, and on a wart that means damaging skin the virus can then seed into. Working out which one you have first is the entire reason this page exists.
Can I have all three at once?
Yes, and it is common. A callus across the ball of the foot, a corn on the little toe and a wart on the arch can happily coexist, which is exactly why people get confused. Work through each lump separately rather than assuming they are all the same thing.
The bottom line
Dots first, skin lines second. Those two settle most cases in under a minute, without touching the thing.
Then the pinch test for anything still unclear. And if the answers point in different directions, that's your cue to show it to somebody who looks at feet all day rather than buying something on a guess.
More: the full corn or wart guide, seed corns explained, and why the little toe gets more corns than any other.
Evan Lewis, PhD, specializes in natural and nutritional therapies for the prevention and management of chronic diseases and their complications. His research spans chronic disease, diabetes complications, clinical nutrition, and nerve health, including the development of topical iodine therapy for foot care and wound health. IodinePure products are listed with Health Canada as cosmetics. This article is for identification and general information, and it is not a diagnosis. Sources: Patil S, Borkar M, Pande S, Meshram K, Oke M. Dermoscopic Findings in Clinically Diagnosed Cases of Plantar Warts, Corns, and Calluses. Cureus. 2023;15(4):e38093. DermNet, Viral wart. NHS, Corns and calluses.
