shedding

Shedding is the process by which an organism loses parts that are worn out or no longer needed. In biology, shedding can refer to the loss of fur, feathers, scales, or skin in animals, the shedding of skin cells in humans, or leaf and fruit abscission in plants. Across taxa, shedding serves growth, development, or defense and is often tightly regulated by hormonal signals.

In animals, shedding includes molting or shedding fur and feathers. Mammals experience hair cycles—anagen, catagen, and telogen—leading to regular hair loss and replacement. Birds molt their plumage to maintain flight and insulation. Reptiles shed or molt their skin in episodes called ecdysis. Shedding can be seasonal or continuous and may be influenced by age, temperature, daylight, nutrition, and reproduction. While largely normal, excessive shedding or patchy loss can indicate dermatologic conditions, parasites, hormonal imbalances, stress, or malnutrition, warranting veterinary evaluation.

In humans, the skin regularly exfoliates as dead cells are shed, typically every few weeks, and scalp hair sheds daily. Pathologic shedding can accompany skin disorders such as psoriasis or eczema, hormonal changes, nutritional deficiencies, or systemic illness. Management focuses on addressing underlying causes and maintaining skin or scalp health.

In plants, abscission is the process by which leaves, fruits, or flowers detach from a plant, often at specialized abscission zones. This is regulated by hormones such as auxin and ethylene and can be triggered by aging, drought, or mechanical damage. Deciduous trees shed leaves seasonally, while fruit drop can be adaptive or stress-induced.