Your Body's Oil Factories: What Glands Produce Oil, What Is Meibum Really Made Of, and How Do We Get It Flowing Again?

By Dr. Sandra Cremers, MD, FACS • Board-Certified Ophthalmologist • Visionary Eye Doctors, Rockville, MD
Harvard Medical School Research Background • Johns Hopkins Affiliated Surgeon

Oil is one of the most underappreciated substances your body produces. Without it, your skin would crack, your ears would be defenseless, and your eyes would dry out within seconds of every blink. Yet most patients — and even many doctors — never stop to think about where all this oil comes from, what it's actually made of at the molecular level, or how we can coax these tiny oil factories back to life when they start to fail.

As an eye surgeon who has spent over 25 years treating meibomian gland dysfunction (MGD) and who was among the first surgeons in the world to insert platelet-rich plasma (PRP) and stem cells directly into meibomian glands, I want to take you on a deep dive into the fascinating biochemistry of human oil production — from head to toe — and then focus on the star of the show: meibum, the remarkable oil that protects your eyes.

Part 1: The Oil-Producing Glands of the Human Body

Your body has several distinct types of glands whose job it is to manufacture and secrete oil or oily/waxy substances. Each has a unique location, a unique secretion, and a unique purpose.

1. Sebaceous Glands (Skin Oil Glands)

Sebaceous glands are the most numerous oil glands in the body. They are found virtually everywhere skin exists — with the highest density on the face, scalp, and upper back (400–900 glands per cm² on the face alone). They are notably absent on the palms and soles. These glands are connected to hair follicles and secrete sebum through a holocrine process, meaning the entire sebocyte cell ruptures and disintegrates to release its oily contents.

Sebum composition (approximate):

Triglycerides & free fatty acids: ~57.5% — the largest fraction, providing lubrication and antimicrobial defense
Wax esters: ~26% — unique to sebum; not found in significant quantities elsewhere in the body
Squalene: ~12% — a polyunsaturated hydrocarbon found only in sebum; acts as an emollient and antioxidant
Cholesterol esters: ~3%
Free cholesterol: ~2%

Sebum also contains the unique fatty acid sapienic acid (a Δ6 isomer of palmitoleic acid), which comprises over 20% of the total fatty acid content and is found nowhere else in the body. Sebum production is driven largely by androgens (puberty/sex hormones—think teen acne), peaks during puberty, and gradually declines after age 70.

2. Meibomian Glands (Tarsal Glands — the Eye's Oil Glands)

Embedded in the tarsal plates of the eyelids, the meibomian glands are modified sebaceous glands — but their secretion, meibum, is biochemically distinct from skin sebum. There are approximately 25–40 glands in the upper lid and 20–30 in the lower lid. Like sebaceous glands, meibomian glands use holocrine secretion: the meibocyte cells fully differentiate, fill with lipid, then rupture to release meibum into the central duct, which opens at the lid margin. We will examine meibum composition in extraordinary detail below.

3. Ceruminous Glands (Ear Wax Glands)

Located in the cartilaginous outer two-thirds of the external auditory canal, ceruminous glands are modified apocrine glands. There are an estimated 1,000–2,000 per ear. They work together with nearby sebaceous glands to produce cerumen (earwax) — a waxy, yellowish-brown substance. Cerumen protects the ear canal from physical damage, traps dust and insects, and contains antimicrobial peptides including β-defensins, cathelicidin, lysozyme, and lactoferrin. Cerumen exists in two genetic types: wet (more common in Caucasians and Africans) and dry (predominant in East Asian populations).

4. Areolar (Montgomery's) Glands

These specialized sebaceous glands surround the nipple in the areola of the breast. They secrete an oily fluid that lubricates and protects the nipple, especially during breastfeeding. They also release volatile compounds thought to serve as an olfactory signal for newborns. These glands enlarge during pregnancy and lactation.

5. Fordyce Spots (Ectopic Sebaceous Glands)

These are sebaceous glands that exist in areas without hair follicles — the lips, the inner cheek mucosa, and the genitalia. They produce sebum that moisturizes these mucosal surfaces.

6. Goblet Cells & the Lacrimal Gland

While not strictly "oil glands," these structures contribute to the tear film alongside the meibomian glands. Conjunctival goblet cells produce the mucin layer, and the lacrimal gland produces the aqueous layer. Together with meibomian oil on top, these three layers form the tri-layered tear film essential for eye health and clear vision.

Part 2: What Is Meibum Really Made Of? A Deep Biochemical Dive

Meibum is one of the most biochemically unique secretions in the entire human body. Its lipid composition is radically different from skin sebum, from the lipids in your blood, and from virtually any other lipid pool found in mammals. Lipidomic studies have identified hundreds of individual molecular species spanning more than a dozen lipid classes.

The Major Lipid Classes of Human Meibum

~90–95% NONPOLAR LIPIDS (the hydrophobic outer layer of the tear film)

1. Wax Monoesters (WE): ~30–40%
These are the single largest class of meibum lipids. A wax ester is formed by a fatty acid bonded to a long-chain fatty alcohol via an ester bond. In meibum, these contain very long-chain fatty acids and fatty alcohols (C18–C30+), many of which are monounsaturated. The predominant fatty acid moiety is oleic acid (C18:1). The chain lengths in meibum wax esters are far longer than those found in skin sebum, which accounts for meibum's higher melting point and unique spreading properties on the tear film.

2. Cholesteryl Esters (CE): ~30–40%
The other dominant class. Cholesterol is esterified with very long-chain fatty acids, often saturated or monounsaturated with chain lengths of C24–C27 (odd and even chains). The most abundant saturated fatty acid moiety is C25:0, followed by C26:0. The predominant monounsaturated species is C24:1. These ultra-long-chain cholesteryl esters are essentially unique to meibum and are not found in significant quantities in blood, sebum, or other body lipids.

3. Wax Diesters (WdiE): ~5–8%
These complex lipids consist of two fatty acid chains esterified to a diol backbone. Recent mass spectrometry studies have identified two subtypes — type 1ω and type 2ω — with type 1ω comprising the most diverse species. Wax diesters are nearly unique to meibum and contribute to its viscoelastic properties.

4. Triacylglycerides (TAG): ~2–5%
Present in relatively small amounts compared to skin sebum (where they dominate at ~45–57%). In meibum, TAGs are a minor but consistent component.

~5–10% POLAR & AMPHIPHILIC LIPIDS (the interface between the oil layer and the aqueous tears)

5. (O-Acyl)-ω-Hydroxy Fatty Acids (OAHFAs): ~4–5%
These are the most important polar lipids in meibum. OAHFAs are amphiphilic — they have both a hydrophobic tail and a hydrophilic head — which allows them to sit at the critical interface between the nonpolar lipid layer and the aqueous tear layer. They act as "molecular surfactants" that stabilize the tear film. Oleic acid (C18:1) is the predominant fatty acid esterified to the ω-hydroxy fatty acid backbone, followed by palmitoleic acid (C16:1). OAHFAs are essentially unique to meibum and tears.

6. Cholesteryl-OAHFAs
A recently discovered class: cholesterol esterified to OAHFAs, creating a hybrid molecule with both structural and surfactant properties.

7. Phospholipids (PL): <0.5%
The presence and quantity of phospholipids in meibum has been historically controversial. Modern high-sensitivity analyses show that phosphatidylcholine (PC) is the predominant phospholipid class, but at very low concentrations (<0.2% by weight in normal controls). Sphingomyelin (SM) is also present in trace amounts. Interestingly, patients with meibomian gland dysfunction show approximately threefold higher PC levels than normal, suggesting a potential biomarker role.

Other Notable Components

Free fatty acids — present in variable amounts; oleic acid predominates
Free cholesterol — small amounts, likely from cell membrane remnants of disintegrating meibocytes
Proteins — found in meibum from patients with MGD at higher concentrations than in normals; may serve as a biomarker of gland instability
Diacylglycerides (DAG) and monoacylglycerides (MAG) — reported in some studies in trace quantities

How Meibum Differs from Sebum: A Quick Comparison

Feature	Skin Sebum	Meibum
Dominant lipids	Triglycerides (~45–57%)	Wax esters + Cholesteryl esters (~60–80%)
Squalene	~12% (unique to sebum)	Absent or negligible
OAHFAs	Not present	~4–5% (critical surfactant)
Fatty acid chain lengths	Shorter (C12–C22)	Very long (C24–C34+)
Wax diesters	Not present	Present (type 1ω and 2ω)
Melting range	Near body temperature	Phase transition ~10–35°C, Tm ~30°C
Unique fatty acid	Sapienic acid (Δ6 C16:1)	Very long-chain OAHFAs

Part 3: What Goes Wrong in Meibomian Gland Dysfunction (MGD)?

In MGD — the leading cause of evaporative dry eye disease worldwide — several key changes occur in the biochemistry of meibum:

Decreased cholesteryl esters: NMR studies show that meibum from MGD patients contains approximately 40% fewer cholesteryl esters than normal meibum. This alters the melting behavior and spreading properties of the oil.
Increased protein content: MGD meibum contains more protein, a biomarker of gland instability and cellular debris from dysfunctional meibocytes.
Reduced unsaturation: There are fewer cis double bonds (cis═CH) and fewer CH₃ (methyl) groups, meaning the lipid chains become straighter and pack more tightly — like butter instead of olive oil.
Increased phospholipids: Threefold increase in phosphatidylcholine, possibly reflecting cellular membrane breakdown.
Higher lipid order (more viscous): The oil becomes thick, waxy, and toothpaste-like rather than flowing freely. This clogs the gland orifices, leading to a vicious cycle of obstruction, inflammation, and eventually gland atrophy (dropout) that is permanent.

The two main pathogenic mechanisms are hyperkeratinization of the ductal epithelium (the duct lining gets thick and plugged) and increased meibum viscosity (the oil itself thickens). Both are worsened by aging, reduced blinking from screen use, contact lens wear, hormonal changes (especially declining androgens), rosacea, and autoimmune conditions like Sjögren's syndrome.

Part 4: Medications and Procedures That Get the Oil Flowing Again

The good news is that we have an expanding arsenal of treatments — from at-home measures to cutting-edge regenerative therapies — designed to restore meibomian gland function and improve the quality and flow of meibum.

At-Home and Nutritional Therapies

Omega-3 Fatty Acid Supplementation (EPA & DHA): Multiple randomized controlled trials and systematic reviews demonstrate that omega-3 supplementation improves meibomian gland function, tear film stability (TBUT), and dry eye symptoms (OSDI scores). Omega-3s work by reducing the omega-6 to omega-3 ratio in red blood cells and plasma, suppressing pro-inflammatory cytokines (TNF-α, IL-1α, IL-1β), and improving the quality and fluidity of meibum itself. High-dose DHA formulations (e.g., 1640 mg DHA + 600 mg EPA daily) showed significant MGD score improvement at 8 weeks. Sources include fish oil, flaxseed oil, and algal DHA.

Warm Compresses & Lid Hygiene: Applying consistent, sustained heat (at least 40°C for 10+ minutes) helps melt thickened meibum and allows it to flow from the glands. Lid scrubs and hypochlorous acid sprays reduce bacterial load and biofilm on the lid margin.

Blinking Exercises: Conscious, full blinks help express meibum from the glands during screen use, when our blink rate and completeness drop dramatically.

Prescription Medications

Oral Doxycycline / Tetracycline (low-dose): These antibiotics have anti-inflammatory properties that improve meibomian gland secretion quality and reduce bacterial lipase activity that degrades meibum.

Anti-inflammatory Eye Drops: Topical corticosteroids (short-term), cyclosporine (Restasis®), and lifitegrast (Xiidra®) reduce the inflammatory cycle at the ocular surface and eyelid margin.

Topical Azithromycin: Applied directly to the lid margin, it reduces bacterial colonization and has anti-inflammatory effects on the glands.

In-Office Procedures

Intense Pulsed Light (IPL) Therapy: Originally discovered serendipitously when rosacea patients reported eye improvement, IPL uses specific wavelengths of light to reduce periocular inflammation, destroy abnormal blood vessels (telangiectasia) that fuel inflammatory mediators to the lid margin, and liquify thickened meibum. Multiple sessions over several months produce cumulative improvement. At our practice, we use the Lumenis OptiLIGHT system.

Thermal Pulsation (LipiFlow® / TearCare®): These devices apply precisely controlled heat to the inner eyelid surface while simultaneously providing gentle pulsed pressure to express blocked meibomian glands. A 12-minute session can clear dozens of obstructed glands at once.

Radiofrequency (RF) Therapy: RF gently heats the eyelids from the outside, liquifying stagnant meibum and reducing inflammation. It can be combined with IPL for synergistic benefit.

Meibomian Gland Expression: Manual expression by your eye doctor, or using specialized tools, physically pushes thickened oil out of the glands, relieving obstruction immediately.

Intraductal Meibomian Gland Probing: Using a fine 1mm probe or cannula inserted directly into the meibomian gland orifice, this procedure breaks through scar tissue and obstructions within the ductal system. It can produce dramatic and sometimes immediate relief.

BlephEx® / Lid Debridement: A handheld device that exfoliates and debrides the lid margin, removing bacterial biofilm, keratinized tissue, and debris from gland openings.

Regenerative Therapies: The Frontier

Platelet-Rich Plasma (PRP) for Meibomian Glands

PRP is prepared from the patient's own blood through centrifugation, concentrating platelets and their rich cargo of growth factors: platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), epidermal growth factor (EGF), and fibronectin. These growth factors stimulate tissue regeneration, reduce inflammation, and may actually help regenerate atrophied meibomian gland tissue.

How PRP is used for dry eye:

PRP Eye Drops: Applied topically 4–6 times daily, PRP drops have been shown in clinical studies to significantly improve tear breakup time, tear meniscus height, and dry eye symptom scores. They may also stimulate regeneration of meibomian gland orifice cells.
PRP Injection into Meibomian Glands: Direct injection of concentrated PRP into the meibomian gland tissue delivers growth factors precisely where they are needed to stimulate gland regeneration and improve oil output.
PRP Injection into Lacrimal Glands: Injection near the lacrimal gland has been shown to improve tear volume and Schirmer test scores.

Clinical evidence shows that PRP reduces pro-inflammatory cytokines (IL-1, IL-6, IL-17, IL-22) that cause lymphocyte infiltration and inflammation of gland orifices. In pilot studies, 25% of eyes showed structural improvement in meibomian gland morphology on meibography after just 4 weeks of PRP therapy.

Stem Cell Therapy for Meibomian & Lacrimal Glands

Mesenchymal stem cells (MSCs) — including adipose-derived MSCs (AD-MSCs) and bone marrow-derived MSCs — represent the next frontier. Research has shown that MSCs injected into or near lacrimal glands can increase tear secretion and decrease tear film osmolarity. In animal models, MSCs have been observed infiltrating eyelid gland tissue, and MSC-derived exosomes have demonstrated anti-fibrosis, anti-inflammatory, and regenerative effects on injured ocular surfaces.

As one of the first surgeons to inject PRP and stem cells into meibomian glands, I am actively conducting clinical research (IRB-approved) on these regenerative therapies for ocular surface disease and systemic inflammatory conditions at our practice through the ART Center.

Part 5: The Bottom Line — Why Meibum Matters

Meibum is a biochemical masterpiece. Its unique combination of very long-chain wax esters, cholesteryl esters, wax diesters, and OAHFA surfactants creates a lipid layer that no artificial tear can truly replicate. This layer prevents your tears from evaporating, provides a smooth optical surface for clear vision, seals your eyelids during sleep, and defends against microbial invasion.

When meibomian glands fail — whether from screen-induced blink suppression, aging, hormonal changes, rosacea, or autoimmune disease — the consequences cascade: unstable tear film → tear hyperosmolarity → epithelial cell damage → neurogenic inflammation → further gland dysfunction. This vicious circle is why early intervention matters.

The exciting news is that we now have tools to break this cycle at every level: omega-3s to improve meibum quality from the inside, IPL and thermal pulsation to clear blockages, and regenerative therapies like PRP and stem cells that may actually restore lost gland tissue. The science of meibum — once an obscure corner of lipid biochemistry — is now driving some of the most innovative treatments in all of ophthalmology.

Selected References

Butovich IA. Historical Brief on Composition of Human Meibum Lipids. Ocul Surf. 2012. PMID: 19635247
Lam SM, et al. Meibum Lipid Composition in Asians with Dry Eye Disease. PLoS One. 2011;6(10):e24339. PMID: 22039991
Borchman D, et al. Differences in Human Meibum Lipid Composition with MGD Using NMR. Invest Ophthalmol Vis Sci. 2012;53(1):337–347. PMC3292369
Miyamoto M, et al. Comprehensive lipid analysis of human meibum and tears. Sci Rep. 2025;15:23048
Chen J, et al. Comprehensive shotgun lipidomics of human meibomian gland secretions. J Lipid Res. 2019;60(5):928–944. PMC6210907
Macsai MS. The Role of Omega-3 Dietary Supplementation in Blepharitis and MGD (AOS Thesis). Trans Am Ophthalmol Soc. 2008;106:336–356. PMC2646454
Murtaza F, et al. Autologous PRP Drops for Evaporative Dry Eye from MGD: A Pilot Study. Clin Ophthalmol. 2022;16:2199–2208. PMC9271282
Alanazi SA, et al. Platelet-rich plasma therapy for MGD and dry eye: A mini review. Biomed Res Ther. 2024. doi:10.15419/bmrat.v11i11.936
Yao L, et al. Mesenchymal Stromal Cell–Based Therapy for Dry Eye. Cell Transplant. 2022;31. PMC9679336
Pappas A, et al. Sebum analysis of individuals with and without acne. Dermatoendocrinol. 2009;1(3):157–161. PMC2835908
Stoeckelhuber M, et al. Human ceruminous gland ultrastructure. Anat Rec. 2006;288A(8):879–884.
Downing DT. Sebaceous gland lipids. Semin Dermatol. 1992. PMID: 1498012

Dr. Sandra Cremers, MD, FACS
Visionary Eye Doctors • 11300 Rockville Pike, Suite 1202, Rockville, MD 20852
Phone: 301-896-0890 • Affiliated with Johns Hopkins Medicine at Suburban Hospital
The Eye Show Podcast • YouTube • TikTok • EyeDoc2020.blogspot.com

This post is for educational purposes only and does not constitute medical advice. Always consult your eye care professional for diagnosis and treatment of dry eye and meibomian gland dysfunction.

Sandra Lora Cremers MD, FACS

Thursday, March 26, 2026

Your eyelids produce life saving oil: Meibum