Corns

Sophie Matzik is a freelance writer for the medical team.

More about the experts All content is checked by medical journalists.

A corn is a localized keratinization of the skin. It is caused by a permanently excessive pressure load or friction, such as that caused by footwear that is too tight. A corneal cone that extends deep into the skin can cause severe pain. Read everything you need to know about the causes, treatment and prognosis of corns here.

ICD codes for this disease: ICD codes are internationally recognized codes for medical diagnoses. They can be found, for example, in doctor's letters or on certificates of incapacity for work. L84

Corn: Description

A corn (clavus, crow's eye, corpse thorn) is a rounded, sharply defined thickening of the skin. In the center sits a hard, tapering corneal cone that extends into the deeper layers of the skin and causes pain when pressed.

Corns are very common. Women, rheumatism and diabetes patients are particularly affected.

Where and how do corns develop?

Corns are caused by constant pressure or friction on the skin. The cause can be, for example, shoes that are too tight or a misaligned foot.

The constant pressure initially causes a callus to form on the foot. The uppermost layers of the skin thicken and keratinize and thus form a protective cushion against permanent external stress. Over time, this increased keratinization (hyperkeratosis) expands into the deeper layers of the skin - a central, keratinized thorn develops.

A corn on the foot (on the sole of the foot or on the sides) is the most common form of clavus. The cause is often pressure loads from splay or flat feet. A corn on the toe is also not uncommon. It is mostly caused by tight shoes. A clavus can even form on the joints or under the toenails. In very rare cases, a corn develops on the finger.

Different types of corn

Doctors differentiate between different forms of corns, which, however, cannot always be precisely delimited from one another in practice. Different types of corns may require different therapies.

• Clavus mollis (soft corn): Found between very tight or deformed toes and has a soft, flat core.
• Clavus durus: A corn with a hard, highly compressed corneal core. Usually forms on the outer foot.
• Clavus subungualis: A corn under the nail.
• Clavus vascularis: A corn that contains blood vessels. This is why it often bleeds when removed.
• Clavus neurovascularis: corn with nerves and therefore very painful.
• Clavus neurofibrosus: A very large corn. The soles of the feet and balls of the feet are particularly affected.
• Clavus papillaris: Is indicated by a white border. In the middle under the corneal layer there is a build-up of fluid, for example a bruise. Hence, this corn is very painful.
• Clavus miliaris: represents a specialty among the corns. It is a matter of many small, not deep, round cornifications that resemble grains of husks and occur mainly in places that are not exposed to any pressure. Since there is no pain with a clavus miliaris, it is also known as a pseudo corn.

Corn or wart?

Corns and warts can be similar to each other. The experienced podiatrist or doctor will recognize the difference immediately.

Warts, like corns, develop in places that are exposed to strong mechanical stress. The most common type is the plantar wart, which is usually located under the cornea and contains small black spots or dots. These are dried bleeding. In contrast to a corn, warts do not have a corneal wedge in the middle and only affect a few layers of the skin, so they are rather flat.

The cause of a wart is a bacterium or virus that invades cracked or injured skin. The most common trigger is the human papillomavirus (HPV).

Corn: Symptoms

A corn shows up as a rounded, sharply demarcated thickening of the cornea which - due to the thick corneal layer - appears yellowish. It is about five to eight millimeters tall.

In the center of the clavus there is a thickened horn (keratin cone) that extends into the deeper layers of the skin in a funnel shape and causes pain when pressed. At first, a small corn is only uncomfortable when walking; Larger corns, on the other hand, can be very painful and restrict those affected in their mobility to such an extent that they can become unable to work.

The tissue around the mandrel can change. Sometimes fluid builds up (edema) or inflammation develops.

If the corneal cone presses on a joint, it can grow together with the surroundings of the joint capsule and cause periosteum irritation or inflammation.

If the corn shows cracks or is scratched open, germs can get inside. These trigger suppuration processes (abscesses) or inflammation. The germs can also spread in the skin (erysipelas) or cause blood poisoning (sepsis).

Corn: causes and risk factors

A corn is formed when skin that is stretched over a bone is continuously exposed to high pressure or friction. The most common cause is wearing shoes that are too tight. Above all tight, tight shoes such as high heels or tight shoes made of hard leather such as pointed boots are dangerous. Because of this, women are also more likely to have corns than men.

Socks that rub against the skin can also cause a corn.

Misalignments of the feet and toes also promote the development of corns. Deformations such as hallux valgus, hammer toes or bony outgrowths (exostoses) place increased stress on individual areas - a corn forms on the foot.

Dry skin, a genetic predisposition to callus formation and certain metabolic diseases are also risk factors for the development of corns. According to the latest findings, radiation treatment (radiation therapy) for cancer can also promote the formation of corns.

Especially in diabetes patients, a corn is a potential entry point for germs and must therefore be treated with particular care.

Corn: examinations and diagnosis

A doctor or experienced medical podiatrist (podiatrist) usually recognizes a corn straight away by its appearance. The keratin cone can be seen with a magnifying glass.

A corn must be delimited from a wart: this can also have excessive keratinization (hyperkeratosis). The very common plantar warts can be distinguished from a corn by the brown spots and bluish-blackish, strip-shaped deposits in their center.

Corn: Treatment

In order to treat a corn successfully and to avoid a relapse (relapse), not only the clavus itself, but - if possible - its cause must also be eliminated. Basically, the following options are available for the treatment of a clavus:

Corn plasters

The most popular treatment method currently is the corn plaster. It has a swab in the middle of its adhesive surface that is soaked in chemicals such as salicylic acid (keratolytics). These soften the thickened corneal layers so that they can then be removed more easily. Corn patches are worn for three to five days. They are available in pharmacies and drugstores.

However, the use of corn plasters is not without risk, especially if you have a corn under your foot, as they can easily slip. The acid on the patch then penetrates the thin, healthy skin next to the corn, where it can cause injuries and inflammation and promote infections. Particular care should be taken by diabetics (who are very susceptible to foot infections), people with circulatory disorders and those with thin, brittle or cracked and dry skin. Experts advise against self-treatment with a corn plaster.

Salicylic drops

As an alternative to the corn plaster, drops containing salicylic can be used. They are applied for several days according to the information provided by the pharmacist or the package insert. After that, the softened cornea can usually be removed without any problems. A hot foot bath makes it easier to remove. To protect healthy skin, it can be covered with cream.

Mechanical removal

It is best to have a corn removed by a doctor, an orthopedic surgeon, or a medical podiatrist (podiatrist). First, the callus is softened in a hot foot bath. Then you remove the excess skin layers with a suitable instrument (such as a milling cutter, scalpel). Hydrogen peroxide is used to soften the core. If the keratin cone is particularly deep, several days of treatment with a corneal dissolving substance may be necessary. A particularly deep corn is surgically removed.

After the clavus has been removed, the affected area should be protected from pressure by foam rings or inserts.

Under no circumstances should you try to cut out the corn yourself with knives or other equipment. The risk of injuries and serious infections is too high!

You can read more about removing corns from the article Removing Corns.

Eliminating the cause

In order to remove a corn sustainably, its cause must also be eliminated as far as possible. You can do a lot yourself:

• Avoid too tight, rubbing shoes.
• During the treatment, the area can be surrounded with small foam rings (corn rings) to relieve pressure. This is also useful in the initial period after the operation. Silicone or foam inserts in the shoe, cotton socks or shoes made from soft materials can provide additional relief.
• Regular washing and lotion keep the skin healthy and resilient.
• If a malaligned foot is the cause of corns, orthopedic insoles, orthopedic shoes or other orthopedic aids can help.

In some cases, a foot deformity is corrected through an operation. The orthopedist decides whether such an operation makes sense or whether orthopedic insoles are sufficient.

Corns in Children

Corns in children need extra care. Corn plasters are not recommended here, as children's skin is still very sensitive and plasters often slip. It is best if the doctor removes corns in children. Then the child should only wear well-fitting shoes.

Corn: disease course and prognosis

Each corn can be completely removed. The earlier a corn is recognized and treated, the better and faster the healing will be. Removing a corn by hand with a knife can leave scars.

Complications

Especially with nerve damage from diabetes mellitus (diabetic neuropathy), the patient may not feel any pain. In such cases in particular, a corn can cause serious complications because the patient recognizes the problem too late or underestimates it. Connections between the skin and an organ (fistulas) or an ulcer (ulcer) can form. Infections can cause tissues on the foot to die (diabetic gangrene).

In order to avoid such complications, diabetics should take good care of their feet or visit a medical podiatrist on a regular basis. You should also show your doctor or podiatrist any change you notice. Because the earlier a corn is treated, the sooner serious consequences can be avoided!

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