Polysorbate 80 vs. polysorbate 20

Polysorbate 80 and polysorbate 20 are close chemical cousins. Both are built on the same polyoxyethylene sorbitan backbone, and the difference is the fatty acid attached to it. NIH’s PubChem database describes polysorbate 20 as a sorbitan monolaurate, made with lauric acid, and polysorbate 80 as a sorbitan monooleate, made with oleic acid. Quell’s label lists Polysorbate 80 (1.0%) as an active ingredient; polysorbate 20 isn’t in it.

What polysorbates are

Polysorbates are a family of ingredients that get along with both water and oil. Their names describe their parts. “Sorbitan” is a ring-shaped core related to sorbitol, a sugar alcohol. “Polyoxyethylene” describes the long chains attached to it, which are friendly to water. The fatty acid, attached at one point, is friendly to oil. One part of the molecule favors water and another favors oil, which is what lets polysorbates sit between the two.

PubChem, the chemistry database run by the National Library of Medicine at NIH, lists both under synonyms that spell out the structure. For polysorbate 20, the entries include “polyoxyethylene (20) sorbitan monolaurate.” For polysorbate 80, they include “POE (20) sorbitan monooleate.” POE is shorthand for polyoxyethylene. Notice that both chemical names carry the same “(20)”: that number belongs to the polyoxyethylene part, and it isn’t the same thing as the 20 or 80 in the everyday name.

Polysorbate 80 vs 20: the fatty acid is the difference

The number in each name points to the fatty acid. PubChem’s records for the two acids show how different they are:

• Lauric acid, used in polysorbate 20, has the formula C12H24O2. Its chemical name is dodecanoic acid: a straight chain of 12 carbons with no double bonds.
• Oleic acid, used in polysorbate 80, has the formula C18H34O2. Its chemical name, (Z)-octadec-9-enoic acid, says it has 18 carbons with one double bond in the middle of the chain.

So polysorbate 80 carries a longer, kinked oil-friendly tail, and polysorbate 20 carries a shorter, straight one. That changes how each balances between water and oil, how it feels in a formula, and which jobs a chemist chooses it for. Neither is simply a stronger or weaker version of the other.

Is polysorbate 80 the same as Tween 80?

Yes, in the sense that “Tween 80” is a trade name for polysorbate 80, and “Tween 20” for polysorbate 20. PubChem lists both trade names among the synonyms. You’ll also see the CAS registry numbers: 9005-65-6 for polysorbate 80 and 9005-64-5 for polysorbate 20. On a drug label, you’ll see the plain name.

Where each one shows up

PubChem’s synonym lists for both run long, full of trade names from different makers, which reflects how many kinds of products use them. Because each has its own fatty acid and its own properties, one can’t be swapped for the other just because the names look alike. Seeing either one on an unrelated product tells you nothing about an eye drop.

For eye drops sold over the counter in the United States, the rule that matters is FDA’s list of permitted lubricant ingredients. Under 21 CFR 349.12, the “liquid polyols” allowed as active demulcent ingredients are glycerin, polyethylene glycol 300, polyethylene glycol 400, polysorbate 80 and propylene glycol. Polysorbate 20 isn’t on that list of active ingredients. This guide doesn’t go further than that, since Quell’s label is the only eye drop label it can speak for.

Polysorbate 80 on Quell’s label

Quell’s Drug Facts panel lists three active ingredients: Glycerol (1.0%), Polysorbate 80 (1.0%) and Light Mineral Oil (0.5%). The label gives the purpose of Polysorbate 80 (1.0%) as lubricant, the same purpose it gives Glycerol (1.0%). Light Mineral Oil (0.5%) is listed as an emollient. The rest of the formula combines a watery base with oils, including emu oil among the inactive ingredients.

Quell is designed to reinforce the tear film’s oil layer to help reduce moisture loss. What does polysorbate 80 do in eye drops covers its role on the label, and polysorbate 80 in eye drops covers how it’s listed.

A laurate on Quell’s label, too

Lauric acid isn’t entirely absent from Quell, but it’s not there as polysorbate 20. The inactive ingredients include glyceryl laurate, which pairs lauric acid with glycerol rather than with a sorbitan backbone. Inactive ingredients aren’t listed for a therapeutic purpose; glyceryl laurate and glyceryl undecylenate explains what they are. The full inactive list reads: Caprylyl Glycol, Dead Sea Salt (Sodium Chloride), Emu Oil, Glyceryl Laurate, Glyceryl Undecylenate, Manuka Honey, Polaxamer 188, Sterile Water, Terminalia Chubula and Tromethamine.

Reading the name on a label

The rule of thumb across the family: the backbone is shared, the fatty acid changes, and the number in the everyday name points to which fatty acid. A label printing “polysorbate” without a number would be incomplete, and the number is what tells you which one a product uses. On Quell’s carton it’s printed in the active ingredients panel, with its strength, as Polysorbate 80 (1.0%).

What to ask if you’re sensitive to an ingredient

If you’ve reacted to a product containing a polysorbate, bring the label to a pharmacist or your eye doctor and ask whether Polysorbate 80 (1.0%) is a concern for you. The Quell label also carries its own caution: Caution should be used in those with egg or bird allergies — For use in the eyes only. Stop and get help if the label’s warning applies: Stop use and ask a doctor if you feel eye pain or changes in your vision, if irritation or redness continues, or if the condition worsens or persists for 72 hours. The Drug Facts page has the whole panel.