2.3 Skin Functions, Sebaceous & Sudoriferous Glands, and the Acid Mantle
Key Takeaways
- Skin functions taught in esthetics include protection, sensation, heat regulation, excretion, secretion, absorption, and vitamin D synthesis.
- The acid mantle is a hydrolipid film commonly taught at about pH 4.5–5.5; stripping it raises transepidermal water loss.
- Sebaceous glands are holocrine, absent on palms and soles, and densest on the T-zone; Meibomian glands are modified sebaceous glands of the eyelids.
- Eccrine glands secrete watery sweat to a surface pore for cooling; apocrine glands empty with follicles in axilla, groin, and areola and activate at puberty.
- Georgia school-kit AHAs must be 3.5 pH or above; medical peels and lasers remain outside O.C.G.A. § 43-10-1(8), and inflamed dermal nodules are referred, not excavated.
What skin does, not just what it is
Physiology is function. Rule 240-16-.02 pairs structure of skin and glands with function. PSI National Domain 2 expects you to know this stack before you analyze a face. Domain 3 (Skin Care) and Domain 6 (Hair Removal) then use the same glands when you massage, extract, or wax.
Functions commonly taught in esthetics (order varies by textbook; this is independent teaching, not a Board-official numbered list):
- Protection — physical (stratum corneum, melanin), chemical (acid mantle, sebum, antimicrobial peptides), biological (Langerhans cells, dermal macrophages).
- Sensation — Merkel cells, Meissner corpuscles, Pacinian corpuscles, free nerve endings for pain and temperature.
- Heat regulation — eccrine sweat, vasodilation and vasoconstriction, fat insulation, limited facial hair.
- Excretion — sweat carries small amounts of salts and nitrogenous waste. It is not a substitute for kidneys. Do not market sweat as medical detox.
- Secretion — sebum, and in a broader sense sweat.
- Absorption — selective; lipid-soluble substances and some actives cross more readily than large water-soluble ones. This is why product chemistry (Chapter 3) and the Georgia school-kit acid floor matter.
- Vitamin D synthesis — cutaneous ultraviolet B (UVB) conversion of 7-dehydrocholesterol. You still recommend daily broad-spectrum sunscreen as home care. You do not prescribe sunbathing as a spa vitamin protocol.
Some texts add wound repair and social touch. Learn the functions your textbooks name. Do not invent a secret official count of “exactly seven PSI items.”
The acid mantle
The acid mantle is the hydrolipid film on the stratum corneum: sebum + residual sweat + corneocyte lipids + metabolites from resident flora. Esthetics commonly teaches surface pH about 4.5 to 5.5 (slightly acidic). It is not stomach acid, and it is not an unpublished item-weight. It is the chemical shield you disturb with high-pH bar soaps and support with correctly formulated toners and moisturizers.
When the mantle is stripped, transepidermal water loss (TEWL) rises, barrier lipids disorder, and opportunistic microbes find it easier to colonize. Clients feel tight, look shiny-flaky, then pick — which becomes your extraction problem the following week.
Georgia connection. Student and apprentice kits may include alpha hydroxy acids at 3.5 pH or above (Rules 240-16-.01 / 240-5-.01). That floor keeps school chemistry milder than medical peels. Medical-depth peels and lasers remain outside O.C.G.A. § 43-10-1(8). If a client hands you a physician-grade peel and asks you to apply it in the salon, decline and refer to the medical setting.
Rule 240-4-.05 forbids double-dipping wax or creams. Every extra dip can inoculate a follicle or sweat pore. Anatomy makes the sanitation rule obvious: glands are holes in the barrier.
Sebaceous glands
Sebaceous glands are holocrine — the cell bursts and dies to become the secretion. The product is sebum: triglycerides, wax esters, squalene, free fatty acids, and some cholesterol. Sebum lubricates hair and skin, feeds the acid mantle, and contributes modest antimicrobial fatty acids.
Distribution. Present wherever hair follicles are; absent on palms and soles. Densest on scalp, forehead, nose, chin (T-zone), and back. That is why comedones cluster where you extract, not on the palms.
Most facial sebaceous glands empty into the pilosebaceous unit (follicle + gland + arrector pili + hair). Some free sebaceous glands are not follicle-associated. Meibomian (tarsal) glands are modified sebaceous glands in the tarsal plate of the eyelids; they secrete the oily layer of the tear film. Heavy, poorly removed product along the lash line disturbs comfort. Lash and brow services (Chapter 10) must respect this anatomy. Do not treat a painful, swollen eyelid margin as a blackhead. Stye- or chalazion-type presentations: stop eye-area service and refer.
Massage and sebaceous skin. Oily, congested skin still has a barrier. Petrissage that slides over inflamed papules can rupture them into the dermis and worsen cysts. Use lighter lymphatic-style strokes over active acne, or skip massage on those maps. You are preparing for safe extraction of open or softened closed comedones, not mashing pustules.
Waxing and the pilosebaceous unit. Wax grips the hair shaft and removes the hair; sebum in the follicle can make adhesion uneven. Do not wax over inflamed acne in the brow. Folliculitis after wax is an infection-control plus aftercare issue (Chapter 9).
Sudoriferous glands
Two types you must separate on sight in a stem:
Eccrine (merocrine) sweat glands. Coiled in the dermis, duct to a sweat pore on the surface, not primarily into the follicle. Distributed widely; concentrated on palms, soles, forehead, and axillae. Secretion is watery sweat (water, salts, small amounts of urea) for thermoregulation, under sympathetic control. A too-hot facial room makes clients drip eccrine sweat that dilutes products and macerates the corneum — turn the steamer down.
Apocrine sweat glands. Associated with hair follicles; concentrated in axillae, groin, and areola. Become active at puberty. Secretion is thicker and odorless until skin bacteria metabolize it. Ceruminous glands (earwax) and mammary glands are modified apocrine relatives — know the family; you are not treating ears or breasts medically as an esthetician.
Anhidrosis (too little sweat) and hyperhidrosis (too much) are conditions, not menu items. Palmar hyperhidrosis affects massage grip and wax adhesion; you adapt technique. Sudden unilateral sweating with neurologic signs: stop and refer.
| Gland | Secretion mode | Duct destination | High-yield sites | Service note |
|---|---|---|---|---|
| Sebaceous | Holocrine | Usually into follicle | T-zone, scalp, back; none on palms/soles | Comedones; do not excavate cysts. |
| Meibomian | Modified sebaceous | Lid margin | Eyelids | Not a facial blackhead; refer lid pathology. |
| Eccrine | Merocrine | Surface pore | Palms, soles, forehead, body | Heat, steam, slippery massage. |
| Apocrine | Apocrine/follicular | With hair follicle | Axilla, groin, areola | Body services; odor after bacterial action. |
Gland disorders you observe — and do not diagnose
Chapter 4 covers acne grades, milia, seborrhea, bromhidrosis, and miliaria. This chapter’s rule: a painful, deep nodule without a clear follicular opening is not an invitation to excavate. Cystic lesions sit in dermis. Georgia law does not authorize you to treat dermatological disease. Refer.
When glands meet the eye. Glands of Moll (modified apocrine) and Meibomian glands live on the lid. Brow waxing that hauls lid skin can inflame them. If the client reports gritty eyes, vision change, or a spreading red lid after a brow service, stop, do not layer more product, and refer.
When to stop during a facial. Honey-crusted weeping, grouped blisters on the lip before extraction, a draining sinus tract in a beard or axilla map, or a client who is febrile with facial cellulitis-type spreading redness — end the service on that area, follow infection-control, and refer. Independent study of gland anatomy exists so you protect the barrier you just learned in 2.1 and 2.2, not so you practice medicine in a Georgia salon.
Which statement best describes the acid mantle for Georgia theory and clinic decisions?
A candidate is asked why palms are not a typical comedone map. What is the correct gland anatomy?
Which pair correctly contrasts eccrine and apocrine sweat glands?
On a Macon clinic facial, a client has a warm, painful nodule on the jaw with no clear opening. What is the correct action?