Apocrine Sweat Glands

1. Overview

Apocrine sweat glands are specialized exocrine glands associated with the skin that produce a viscous, protein-rich secretion. Unlike eccrine glands, which function primarily in thermoregulation, apocrine glands are involved in scent release and become active during puberty. Their secretions are initially odorless but can develop a characteristic body odor upon bacterial decomposition. Apocrine glands are part of the integumentary system and play roles in emotional sweating, pheromone signaling, and possibly sexual attraction.

2. Location

Apocrine glands are primarily located in specific regions of the body, including:

• Axillae (armpits)

• Areolae of the nipples

• Anogenital region

• External auditory canal (ceruminous glands, a modified form)

• Eyelids (Moll’s glands, another modified form)

They are typically associated with hair follicles and are found deep in the dermis or upper hypodermis, opening into the hair follicle canal rather than directly onto the skin surface.

3. Structure

Apocrine sweat glands are large, coiled tubular glands with the following features:

• Secretory portion: Located deep in the dermis or subcutaneous tissue, lined by a single layer of cuboidal or columnar epithelial cells surrounded by myoepithelial cells.

• Duct: Shorter and straighter than eccrine ducts; empties into the upper part of the hair follicle.

• Myoepithelial cells: Contractile cells that assist in expelling the secretion into the duct system.

Unlike the name suggests, apocrine secretion is mostly merocrine in humans (exocytosis without loss of cytoplasm), though some loss of membrane may occur.

4. Function

Apocrine glands have distinct roles compared to eccrine glands:

• Produce a thick, milky secretion composed of proteins, lipids, steroids, and pheromone-like compounds.

• Respond to emotional and adrenergic stimuli such as stress, fear, pain, or sexual arousal—not thermoregulatory triggers.

• Contribute to individual body scent after microbial breakdown of their secretions on the skin surface.

Their activity is minimal during childhood and increases significantly at puberty due to androgen stimulation.

5. Physiological role(s)

Although not essential for temperature control, apocrine glands serve several important physiological roles:

• Chemical communication: Secretion may contain pheromone-like substances that influence human behavior, sexual attraction, and social interaction.

• Emotional sweating: Secretion is triggered during emotional stress or arousal, potentially enhancing grip or acting as a nonverbal cue.

• Protective lubrication: In areas like the external auditory canal (ceruminous glands), apocrine secretion helps trap debris and protect the eardrum.

• Sexual and reproductive signaling: Evolutionarily, apocrine secretions may have contributed to mate selection in primates via scent cues.

6. Clinical Significance

Apocrine glands are involved in several clinical and dermatological conditions:

• Body odor (bromhidrosis):

  • Results from bacterial decomposition of apocrine secretions in areas like the axillae.

  • Managed with hygiene, antiperspirants, antibacterial agents, or botulinum toxin injections.

• Hidradenitis suppurativa:

  • A chronic, inflammatory skin condition involving apocrine glands, especially in the axillary and groin areas.

  • Presents with painful nodules, abscesses, and scarring; may require antibiotics, surgery, or immunomodulatory therapy.

• Fox-Fordyce disease:

  • A rare condition involving pruritic papules over apocrine-rich areas, likely due to ductal obstruction.

• Apocrine tumors:

  • Rare benign (e.g., apocrine hidrocystoma) or malignant tumors arising from apocrine glands.

  • May present as nodules or cysts in the axilla or other apocrine-rich areas.

• Hyperhidrosis:

  • Although more often related to eccrine overactivity, apocrine hyperfunction can contribute to emotional sweating and discomfort.