Demulcent vs. emollient eye drops

A demulcent is a water-friendly lubricant, usually a polymer, that coats and soothes the eye’s surface; an emollient is a fat or oil that protects and softens. FDA’s over-the-counter eye drop rules, 21 CFR Part 349 (now published as OTC Monograph M018), list glycerin and polysorbate 80 as demulcents and light mineral oil as an emollient. Quell contains all three.

The short version, side by side

• Made of: demulcents are usually water-soluble polymers or liquid polyols; emollients are usually fats, oils or waxes.
• On the label: a demulcent’s purpose is usually printed as “lubricant,” an emollient’s as “emollient.”
• In the tear film: demulcents mix into the watery part of tears; emollients belong with the oil.
• In products: thick eye ointments are built mainly on emollients such as petrolatum, many drops rely on demulcents alone, and some drops combine the two.
• In the regulation: demulcents are listed in 21 CFR 349.12, emollients in 349.14.

How the regulation defines each

Section 349.3 of the federal rules gives both definitions. A demulcent, in its words, is usually a water-soluble polymer, applied topically to the eye, that protects and lubricates mucous membrane surfaces and relieves dryness and irritation. An emollient is usually a fat or oil, applied locally to the eyelids, that protects or softens tissues and keeps them from drying and cracking.

Notice the difference in target. The demulcent definition is about the surface of the eye; the emollient definition is written around the eyelids, which reflects how many emollient products are thick ointments. Light mineral oil is a thinner oil than petrolatum, and in Quell it’s part of a drop rather than an ointment.

The two lists, by group

Glycerin and polysorbate 80 both sit in 349.12’s liquid polyols group, next to propylene glycol and two polyethylene glycols. The same section also covers the cellulose derivatives, such as hypromellose, along with polyvinyl alcohol, povidone, gelatin and dextran 70. Light mineral oil sits in 349.14’s oleaginous, or oily, group with mineral oil, petrolatum, paraffin and waxes; the only other emollient group is lanolin.

Where each one works in the tear film

The tear film has three layers: a mucus layer against the eye, a watery middle, and a thin oil layer on top that slows evaporation. A demulcent dissolves in water, so it joins the watery part of tears and makes it slipperier. An emollient is an oil, so it doesn’t dissolve in water; it goes where the oil goes, on top.

That’s why a formula might include both. Quell is designed to reinforce the tear film’s oil layer to help reduce moisture loss, and it pairs two demulcents with one emollient: Glycerol (1.0%), Polysorbate 80 (1.0%) and Light Mineral Oil (0.5%). The tear film’s oil layer, explained covers that top layer in more depth.

How to tell which is in a drop

Turn the box over and find the Drug Facts panel. The active ingredients section lists each active with its strength and its purpose. Read the purpose column:

• “Lubricant” beside an ingredient usually means a demulcent from 349.12.
• “Emollient” means an ingredient from 349.14.
• If every active is a lubricant, the drop is demulcent-only.
• If there’s at least one emollient, the drop contains an oil and may look cloudy or milky instead of clear.

Quell’s panel follows that pattern, and its look reflects the oil: The eye drops have a naturally milky-brown appearance. This is normal and does not indicate a problem with the product. The active ingredients on an eye drop label walks through the layout line by line.

Does one work better than the other?

Neither category wins in general. They do different jobs, and which drop suits you depends on what your eyes need, a question for an eye doctor if dryness keeps coming back. What a label can tell you is what’s in the bottle and what it’s for. Quell’s stated Uses are “For use as a protectant against further irritation or to relieve dryness of the eye.”

Demulcents and emollients in drops vs. ointments

Many eye ointments are mostly emollient, built on petrolatum or mineral oil, which is why they’re thick and can blur vision for a while after use. Drops are mostly water, with demulcents dissolved in them and, in some formulas, a small amount of oil. Eye drops vs. eye ointment compares the two forms.

Going deeper on each

Each side has its own guide: what is a demulcent in eye drops? for the water-friendly ingredients and emollient eye drops for the oily ones. The Drug Facts page shows Quell’s full panel, including inactive ingredients such as emu oil.