callus

Callus is a term used in biology to describe two related but distinct phenomena. In human anatomy, a callus is a thickened area of skin that develops in response to repeated friction or pressure. In botany, a callus is a mass of undifferentiated plant cells that forms at wound sites or in cultured tissue and can give rise to new tissues.

Caused by mechanical irritation, skin calluses involve an increase in keratinocyte production and thickening of the stratum corneum. They commonly occur on hands and feet, particularly on weight-bearing surfaces or areas subjected to repetitive rubbing, such as the palms, fingers, soles, and under callous formation from ill-fitting footwear. Calluses are usually benign and painless, but they can become sensitive or inflamed if pressure continues.

Management focuses on reducing friction and thickened skin. Protective padding, properly fitting footwear or gloves, and regular gentle abrasion or filing by a professional can help. Keratolytic agents containing salicylic acid or urea may be used with caution, especially under professional supervision, to soften the inner layers. People with diabetes or poor circulation should avoid self-treatment and seek medical advice if there is any redness, swelling, open sores, or persistent pain.

In plants, callus refers to a loose, unorganized mass of parenchymal cells produced by de-differentiation in response to wounding or hormonal cues. In tissue culture, callus tissue is typically induced by an excess of auxin relative to cytokinin, and can be induced to differentiate into shoots, roots, or embryos under adjusted hormone conditions. Callus formation is a key feature of plant cell totipotency and is widely used in micropropagation, genetic transformation, and somatic embryogenesis.