Corns (Clavus): causes, treatment, prevention
A corn is a local cornification of the skin. It is caused by a permanently excessive pressure load or friction, such as that caused by shoes that are too tight. A corneal cone reaching deep into the skin can cause severe pain. Read all about the causes, treatment and prognosis of corns here.
A pigeon’s eye (clavus, crow’s eye, light thorn) is a roundish, sharply defined thickening of the skin. In the centre of corns there is a hard, tapering corneal cone which reaches into deeper layers of the skin and causes pain when pressure is applied.
The corn is very common. Women, rheumatism and diabetes patients are particularly affected.
Where and how do corns develop?
Corns are caused by permanent pressure or friction on the skin. The cause can be, for example, too tight shoes or a foot malposition.
Due to the constant pressure, a callus initially forms on the foot. The uppermost skin layers thicken and keratinize, thus forming a protective cushion against permanent external stress. Over time, this increased keratinization (hyperkeratosis) extends into deeper skin layers and a central, keratinized thorn is formed.
A corn on the foot – on the sole or sides – is the most common form of Clavus. This is often caused by pressure loads from a splay foot or flat foot. A corn on the toe is also not uncommon, usually caused by tight shoes. A clavus can even form on the joints or under the toenails. In very rare cases, a corn eye develops on the finger.
Different types of corn
Doctors distinguish between different forms of corns, but in practice it is not always possible to distinguish between them. Different types of corns may require different therapies.
- Clavus mollis (soft corn): Is found between very tightly standing or deformed toes and has a soft, flat core.
- Clavus durusA cornea with a hard, highly compressed corneal nucleus. It is usually located on the outer foot.
- Subungualis clavusA corn under the nail.
- Clavus vasculare: A corn in which there are blood vessels. Therefore it often bleeds when removed.
- Clavus neurovasculare: With nerves penetrated corn and therefore very painful.
- Clavus neurofibrosum: A very large corn. The sole and ball of the foot are mainly affected.
- Clavus papillaris: Is marked by a white border. In the middle under the corneal layer there is an accumulation of fluid, for example a bruise. Therefore this corn is very painful.
- Clavus miliaris: Represents a speciality among corns. It is a not deep reaching, round keratinization, which occurs mainly in places that are not exposed to pressure. Since there is no pain in a Clavus miliaris, it is also called pseudo corn.
Corn or wart?
Corns and warts can resemble each other. However, the experienced chiropodist or doctor will immediately recognise the difference.
Warts, like cornrows, 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 spots. These are dried bleedings. In contrast to a cornea, warts do not have a corneal wedge in the middle and only affect a few layers of skin, so they are rather flat.
The cause of a wart is a bacterium or virus that penetrates cracked or injured skin. The most common trigger is the human papillomavirus (HPV).
A cornea appears as a roundish, sharply defined corneal thickening, which – due to the thick corneal layer – appears yellowish. It is about five to eight millimetres in size.
In the centre of the clavus there is a thickened horn (keratin cone), which extends funnel-shaped into deeper skin layers and causes pain when pressure is applied. A small corn is initially only uncomfortable when walking; larger corns, on the other hand, can be very painful and restrict the affected person’s mobility to such an extent that occupational disability can result.
The tissue around the mandrel can change. Sometimes fluid accumulates (edema) or an inflammation develops.
If the corneal cone presses on a joint, it can fuse with the area surrounding the joint capsule and cause irritation or inflammation of the periosteum.
If the corn has cracks or is scratched open, germs can get inside. These trigger suppurative processes (abscesses) or inflammations. The germs can also spread in the skin (erysipelas) or cause blood poisoning (sepsis).
Corn: causes and risk factors
Cornification occurs when skin stretched over a bone is permanently exposed to high pressure or friction. The most common cause is wearing shoes that are too tight. Especially tight, pressing shoes like high heels or tight shoes made of hard leather like pointed boots are dangerous. For this reason, women also have corns more often than men.
Socks that rub on the skin can also cause cornification.
In addition to unsuitable footwear, malpositioning of the feet and toes also promotes the development of corns. Deformations such as hallux valgus, hammer toes or bony outgrowths (exostoses) put increased strain on individual areas – a cornucopia forms on the foot.
Dry skin, a genetic predisposition to corneal formation and certain metabolic diseases are also risk factors for the development of corns. According to the latest findings, radiotherapy for cancer patients can also promote the formation of corns.
Particularly in diabetes patients, corn is a potential entry point for germs and must therefore be treated particularly carefully.
Corn: examinations and diagnosis
A doctor or experienced medical chiropodist (podiatrist) usually recognizes a corn by its appearance at first glance. The keratin cone can be identified with a magnifying glass.
A corn eye must be distinguished from a wart: excessive keratinization (hyperkeratosis) can also occur in them. However, the very common plantar warts can be distinguished from a corn by the brown spots and bluish-blackish, stripy deposits in their centre.
In order to successfully treat a corn and prevent a relapse (recurrence), not only the clavus itself but also its cause must be eliminated.
There are several possibilities for the treatment of a clavus:
The currently most popular treatment method is corn plaster. They have a swab in the middle of their adhesive surface which is soaked with chemicals such as salicylic acid (keratolytics). These soften the thickened corneal layers so that they can then be removed more easily. Corn plasters are worn for three to five days. They are available at the pharmacy and drugstore.
However, especially with a corn under the foot, the use of corn plasters is not without danger, as they can easily slip. The acid on the patch then penetrates into 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 (are very susceptible to foot infections), people with circulatory problems and people with thin, brittle or cracked and dry skin. Experts advise against self-treatment with a corn plaster.
Salicyl-containing drops can be used as an alternative to corn plaster. According to the information provided by the pharmacist or the package leaflet, these are applied for several days. The softened cornea can then usually be removed. A hot footbath facilitates the removal. To protect healthy skin, it can be covered with cream.
It is best to have a corn removed by a doctor, an orthopaedic surgeon or a medical chiropodist (podiatrist). For this purpose, the cornea is softened in a hot foot bath before the excess skin layers are removed with a suitable instrument (such as a milling cutter or scalpel). Hydrogen peroxide is used to soften the core. If the keratin cone is particularly deep, treatment with a corneal dissolving substance over several days may be necessary. A particularly deep-seated corn is surgically removed.
After removal of the clavus, the affected area should be protected from pressure by foam rings or inserts.
Affected persons should never try to cut out the corn themselves with knives or other devices, because then injuries or serious infections usually occur.
You can read more about removing corns in the article Remove corn.
In order to remove a corn permanently, its cause must also be eliminated. There is a lot you can do yourself: in future, avoid wearing too tight, rubbing shoes. During treatment, the area can be surrounded with small foam rings (corn rings) and thus relieved of pressure. This is also useful in the initial period after the operation. Silicone or foam inserts in the shoe, cotton socks or shoes made of soft materials can provide additional relief.
Regular washing and moisturising of the skin is also important, as this keeps the skin healthy and resistant.
If a foot malposition is the cause of corns, orthopaedic insoles, orthopaedic shoes or other orthopaedic aids can help. In some cases, a foot malposition is corrected by surgery. The orthopaedic surgeon decides whether such an operation is sensible or whether orthopaedic insoles are sufficient.
Corns in children
Corns in children must be treated with special care. Corn plasters are not recommended here, as children’s skin is still very sensitive and plasters slip very often. It is best if corns are removed by the doctor in children. Afterwards the child should only wear well-fitting shoes.
Corn: course of disease and prognosis
Each corn can be completely removed. The earlier a corn is detected and treated, the better and faster the healing process. If a corn is removed by hand with a knife, scars may remain.
Especially in the case of nerve damage caused by diabetes mellitus (diabetic neuropathy), patients may not feel any pain. Especially in such cases, a corn may bring serious complications, because the problem is recognized too late or underestimated. Connecting passages between the skin and an organ (fistulas) or an ulcer (ulcer) can form. Infections can cause tissue on the foot to die off (diabetic gangrene). Diabetics should therefore take special care of their feet and show any changes to their doctor or medical chiropodist. The earlier a corn is treated, the sooner serious consequences can be avoided!