What's Are Calluses? How Do They Differ from Other Skin?

Ordinary calluses are thickenings of the skin typically found on hands and feet through ordinary rubbing or friction. This form of callus is generally harmless and is often associated with poorly fitting footwear or repeated actions perhaps as a result of an occupation. Writers may develop a callus on their middle finger. Carpenters may develop a number of calluses on their fingers and palms, if the rubbing is gradual and repeated (if it occurs quickly-over only a short period of time-a blister results).

Keratinocytes

Palmar skin (skin associated with the palms of the hands) is approximately 0.8 to 1.4 mm thick-about ten times as thick as most other skin. Plantar skin-skin of the soles of the feet-is also thick, heavily keratinized. What does "keratinized" mean? Skin, with its high degree of complexity, includes a variety of cell types called keratinocytes. Keratinocytes accumulate on the surface or "horny layer" of skin, where they serve to protect the inner layers.

Keratin - What It Is - Where It Is Found

Gradual, repeated friction and rubbing, stimulates these cells to produce a tough, fibrous, form of protein called keratin which toughens skin by producing calluses. Keratin is further strengthened by the formation of disulfide bonds between individual molecules to form a kind of network. Consider the strength and durability of animal beaks and claws-the horn of the rhinoceros!

Interestingly, some have heard the story that horses hooves and other sources of keratin are used to make the gelatin one finds in human food. The Gelatin Manufacturer's Institute of America however, assures us that gelatin is not made from keratin.

Treating Calluses

Sometimes calluses become excessive and unattractive, and thus need treatment to reduce or eliminate their presence or appearance. What are some of the methodologies for doing so? On the feet, soaking in water, followed by gentle sanding with a pumice stone may be very successful in removing layers of callused tissue. There are medications containing such ingredients as salicylic acid, and of course minor surgeries. Such treatments work well, but should be performed only under expert care for persons with diabetes. Consult a physician, such as a podiatrist in those instances.

References and Resources:

Molecular Expressions - Palmar Skin

Molecular Expressions - Plantar Skin

NCBI - Keratinocytes

Yes Mag - "What is a rhinoceros horn made of?"