The sebaceous glands are tiny, oil-producing structures in the skin that secrete a lipid-rich substance known as sebum. They occur in greatest density on the face and scalp but are present over most of the body except the palms of the hands and soles of the feet. Most sebaceous glands are associated with hair follicles to form the pilosebaceous unit; others, such as the meibomian glands of the eyelids, discharge directly into specialized ducts. For an overview of microscopic anatomy, see microscopic glands.

Structure and secretion

Sebaceous glands are classified as holocrine glands: their secretory cells accumulate lipid and then disintegrate to release sebum. The secretion is a complex mixture of triglycerides, wax esters, squalene and cholesterol derivatives, together with cellular debris. Most glands open into the upper portion of the hair follicle; some—called sebaceous follicles—open directly onto the skin surface. The eyelid meibomian glands produce a thicker, specialized lipid that helps stabilize the tear film. For anatomical references, consult gland anatomy and pilosebaceous unit.

Development and regulation

Sebaceous glands develop from epidermal (skin) tissue during fetal growth as appendages of hair follicles. Their activity is tightly regulated by hormones: androgens (male sex hormones) stimulate sebum production, which explains the marked increase in sebum output during puberty. Production typically peaks in adolescence and may decline with age. External factors such as cleansing agents and water temperature also influence the amount of surface sebum; vigorous washing with detergents can reduce oily residues, while warm water above roughly 29 °C (84 °F) keeps sebum more fluid during washing. See more on development and regulation at gland development, hormonal effects, and temperature and cleansing.

Functions and importance

Sebum contributes several practical functions for the skin and hair: it lubricates and softens keratinized tissue, provides a degree of waterproofing, and influences the surface microbiome by creating a lipid environment favored by some commensal microbes. These roles affect skin texture, hair sheen, and the barrier that limits water loss. Excessive or deficient sebum production can have cosmetic and medical consequences, and many dermatologic treatments target sebum production directly. For functional details, see sebum composition, skin barrier, and microbial interactions.

Clinical conditions and distinctions

Because the sebaceous gland is central to several common skin conditions, it is of interest to both primary care and dermatology. Typical issues include:

  • Acne vulgaris: a multifactorial condition involving increased sebum, follicular keratin plugging and bacteria such as Cutibacterium acnes, leading to inflammation.
  • Sebaceous cysts (often epidermal inclusion cysts) and sebaceous hyperplasia: benign enlargements or blocked follicles producing palpable lumps.
  • Sebaceous adenomas and carcinomas: rare benign or malignant tumors of sebaceous origin; eyelid (meibomian) carcinomas are an important example and require specialist assessment.
  • Genetic associations: certain syndromes link sebaceous neoplasms with internal cancers; clinicians may investigate such associations when tumors are unusual.

Management strategies range from topical cleansers, retinoids and antimicrobial agents for acne to surgical excision for cysts and tumors. Systemic therapies such as isotretinoin markedly reduce sebum production and are reserved for severe disease. Practical advice about hygiene and products that affect sebum is available at skin care, while clinical treatment options are summarized at dermatologic therapy and surgical management.

Notable distinctions include the difference between sebaceous glands and sweat glands (eccrine and apocrine): sebaceous glands produce oily secretions and are mostly linked to hair follicles, whereas sweat glands primarily produce watery sweat for thermoregulation. Understanding sebaceous gland biology helps explain common dermatologic patterns and guides appropriate treatment for oily skin, acne, and glandular tumors.