What Is a Foot Callus and Why Does It Form?
What Is a Foot Callus and Why Does It Form?
By Sylke Bommel Ā· Updated August 2026 Ā· 7 min read
Key Takeaways
- A callus is hyperkeratosis, a buildup of skin cells and thickened outer skin layer triggered by repeated pressure or friction, and it is a genuinely protective response, not a disease.
- In one clinical study of older adults, plantar pressure under callused areas of the forefoot was up to 14% higher than under uncallused skin at the same anatomical sites.
- Calluses form where mechanical stress is highest during standing and walking, most often the heel and the ball of the foot.
- Skin cells called keratinocytes sense mechanical pressure and respond by multiplying faster and building up extra layers of protective keratin.
- A callus only becomes a problem once it grows thick enough to cause pain itself, at which point it is treated rather than simply left alone.
What Is a Callus, Exactly?
A callus is an area of thickened skin caused by hyperkeratosis, an increase in keratinocyte activity triggered by chronic pressure or friction.
In callused skin, the stratum corneum and stratum granulosum, the outer layers of skin, become measurably thicker, while the density of individual keratinocytes within that thickened layer actually decreases. In plain terms, the skin builds more layers of protective material in response to repeated stress, even though each individual cell layer is somewhat less densely packed.
This is fundamentally different from an infection, injury, or disease process, a callus is skin doing exactly what it is designed to do when faced with repeated mechanical demand.
Why Does Skin Respond to Pressure This Way?
Skin responds to repeated pressure by thickening because keratinocytes, the primary cells of the outer skin layer, are able to sense mechanical stress and respond to it directly.
These cells relay mechanical signals through mechanosensitive receptors, triggering a cascade that increases keratinocyte proliferation and accelerates how quickly new skin cells are produced and pushed toward the surface. Over time, this results in a visibly and measurably thicker area of skin exactly where the repeated pressure or friction is occurring.
This response evolved as protection, thicker skin is more resistant to the blistering and tissue damage that repeated friction would otherwise cause, which is why calluses reliably form at the body's highest-friction, highest-pressure contact points.
Does Pressure Really Cause More Callus Buildup?
Yes, and this relationship has been directly measured in clinical research rather than just assumed.
A study of nearly 300 older adults found that plantar pressure under callused regions of the forefoot was significantly higher than under uncallused skin at the same anatomical sites, up to roughly 14% higher at some measurement points. Researchers propose that this raised pressure accelerates keratinocyte turnover in the epidermis, meaning higher pressure and callus formation likely reinforce each other over time.
This helps explain why calluses tend to return in the same location if the underlying pressure source, whether footwear, gait, or foot structure, is not addressed alongside removal.
Callus Formation: Protective vs Problematic
The table below distinguishes when callus formation is simply a normal protective response versus when it becomes something to actively manage.
| Protective (Normal) | Problematic (Needs Attention) |
|---|---|
| Mild, even thickening at pressure points | Thick buildup causing pain when walking |
| No pain or discomfort | Cracking, bleeding, or signs of infection |
| Manageable with routine home care | Rapidly recurring despite consistent care |
Most calluses stay in the protective category for most people, they only need active management once they cross into causing pain or other complications.
Where Do Calluses Typically Form and Why?
Calluses most often form on the heel and the ball of the foot, specifically under the metatarsal heads, since these are the points that bear the most pressure during standing and walking.
Ill-fitting shoes, an uneven gait, or bony prominences in the foot can concentrate pressure onto smaller areas than normal, which is why calluses sometimes appear in less typical spots as well. Understanding that location follows pressure is genuinely useful, since it points directly at what needs to change, footwear fit, gait, or pressure distribution, if a callus keeps rebuilding quickly.
A softening product like Imperial Feet's Callus Softener Spray can help loosen thickened skin at these common pressure points ahead of gentle filing, making regular maintenance easier at exactly the areas most prone to buildup.
When Does a Callus Need Attention?
A callus needs attention once it becomes painful, grows thick enough to affect how you walk, or shows signs of cracking or infection.
Up to that point, a callus is simply skin doing its job, and aggressive removal of a thin, painless callus is not necessary and can even be counterproductive if it disrupts the skin's natural protective response. People with diabetes, poor circulation, or reduced sensation should have any callus monitored by a podiatrist rather than self-treating, since reduced feeling can allow a callus to progress to a deeper problem unnoticed.
For most people, routine softening and gentle filing, done consistently, keeps calluses comfortable and manageable without needing more aggressive intervention.
14%
In a clinical study of nearly 300 older adults, plantar pressure under callused areas of the forefoot was up to 14% higher than under uncallused skin at the same sites, published in Clinical and Experimental Dermatology.
Understanding Your Callus Checklist
- āCheck whether the callus is painful or just present without discomfort
- āNote its location, since this points to the underlying pressure source
- āConsider whether footwear fit could be contributing to the pressure
- āSoften and gently file if it's uncomfortable or growing thick
- āSee a podiatrist if it's painful, cracking, or you have diabetes or poor circulation
ā ļø Note: if you have diabetes, poor circulation, or reduced sensation in your feet, have a podiatrist monitor any callus rather than self-treating, since reduced feeling can allow problems to progress unnoticed.
Callus Softener Spray
Callus Softener Spray helps loosen thickened skin at common pressure points like the heel and ball of the foot, making gentle, regular maintenance easier.
View Callus Softener SprayFrequently Asked Questions
Is a callus a sign that something is wrong with my feet?
Not necessarily. A callus is a normal, protective response to repeated pressure or friction. It only signals a potential issue, like footwear fit or gait, when it becomes painful, grows very thick, or rebuilds unusually quickly.
Why do calluses form in the same spot over and over?
Calluses return in the same location because the underlying pressure or friction causing them, often from footwear, gait, or a bony prominence, has not changed. Addressing that source alongside removal reduces how quickly they rebuild.
Do calluses actually increase pressure on the foot?
Research suggests the relationship goes both ways. Higher pressure contributes to callus formation, and once a callus forms, studies have measured meaningfully higher plantar pressure under that thickened area compared to surrounding skin.
Should I remove every callus I have?
Not necessarily. A thin, painless callus is simply skin doing its protective job and does not need aggressive removal. Focus on managing calluses that are uncomfortable, thick, or causing problems with your gait.
Can callus formation be prevented entirely?
Since calluses form in response to real mechanical pressure, some buildup at high-pressure points like the heel and ball of the foot is a normal part of how skin adapts. Well-fitted footwear and routine care can keep this manageable rather than eliminating it completely.
Clinical Sources
- Freeman DB. Corns and calluses resulting from mechanical hyperkeratosis. Am Fam Physician. 2002;65(11):2277-2280.
- Menz HB, Zammit GV, Munteanu SE. Plantar pressures are higher under callused regions of the foot in older people. Clin Exp Dermatol. 2007;32(4):375-380.
- Al Aboud AM, Yarrarapu SNS. Corns. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jul 24. PMID: 29262147.
- DermNet NZ. Corns and calluses (heloma, tyloma). dermnetnz.org/topics/corn-callus
Related Reading
Owner, Imperial Feet ā Third-Generation Foot Care
Sylke Bommel is the owner and third-generation leader of Imperial Feet, the Dutch professional foot care brand her grandfather founded in 2001. Raised in Aruba and based in Haarlem, just outside Amsterdam, she has led the brand's international expansion for over a decade, growing Imperial Feet from a single Dutch distributor to a professional range used by pedicurists, podiatrists, and pharmacies in more than 20 countries, including the United States.
Editorial note: Sylke writes from the perspective of a foot care brand owner and formulator, not a medical practitioner. Content is educational and does not replace individual medical advice from a qualified foot care professional.
Disclaimer: This article is for informational purposes only and does not replace individual medical advice from a qualified foot care professional. If you have diabetes, poor circulation, or a persistent infection, consult a podiatrist before self-treating.
