Definitive Collection / New
One Serum.
Once a Night.
Definitive Lash Serum is a peptide treatment for visibly longer, fuller, stronger-looking lashes. Five actives at the root and along the fiber. No prostaglandin analogs, no hormones.
The Lash.
Lengthening and strengthening treatment. Once daily, PM, along the upper lash line.
explore the formula
Behind the Lash Serum
A lash is hair. It has a root, a growth cycle and an anchor. Age, friction, extensions and mascara removal shorten the cycle and loosen the anchor. Definitive Lash Serum was formulated to work at both, with peptides and a plant biotech active at the follicle and amino acids and biotin along the fiber.
Five actives, five separate jobs
- up to 27%lash density, 8 wks
Peptide and Red Clover Complex
Density and anchorage at the follicle - +23%lash diameter, 60 days
Lash Diameter Peptide
Thickness and strength of the fiber - Anchorlaminin 5, collagen IV
Biotin-Peptide Complex
Hold at the root, length and diameter - +177%papilla cell activity, in vitro
Phyto-Peptide Complex
Follicle vitality, a longer growing phase - Conditionmoisture and luster
Amino Acid Conditioning Complex
Flexible, hydrated lashes that stay
Supplier studies on the individual active at the stated concentration, not a finished-product trial. Results vary.
What is not in it
Read the back of the other tube first.
The fastest-acting lash serums on the market contain a synthetic prostaglandin analog. On an ingredient list it reads as isopropyl cloprostenate, dechloro dihydroxy difluoro ethylcloprostenolamide, methylamido dihydro noralfaprostal or norbimatoprost.
These are the same class of molecule as the active in prescription lash drugs. The known effects include darkening of the iris, which can be permanent, darkening of the eyelid skin, loss of fat around the eye that hollows the socket, and redness or itching. Health Canada prohibits them in cosmetics. In February 2026 the EU scientific committee concluded three of them cannot be considered safe for cosmetic use.
Definitive Lash Serum contains none of them. It contains no hormones and no progesterone. It is built to be used every night for years, on the eye, which is the only place a lash serum goes.
No prostaglandin analogs
No isopropyl cloprostenate, no ethylcloprostenolamide, no norbimatoprost, no dehydrolatanoprost.No hormones
Progesterone-free. No hormonal actives of any kind.No iris or eyelid darkening risk
The pigmentation effect is associated with prostaglandin analogs. Without them, that risk does not apply.No fragrance, no oil
A clear, weightless serum that dries quickly and sits under eye cream.
Sources: US FDA warning letter on isopropyl cloprostenate (2011); Latisse prescribing information; Health Canada Cosmetic Ingredient Hotlist; EU SCCS opinion SCCS/1680/25 (2 February 2026).
What to expect
Results follow the lash cycle, not the calendar.
A lash takes weeks to grow. New growth is visible only once it clears the lid, so the first change most people notice is that fewer lashes are on the cotton pad.
Hold
Fewer lashes shed on removal. The fringe feels softer and more flexible.
Density
First visible change at the root: the lash line reads fuller, especially at the outer corner.
Length
New lashes clear the lid and reach full length. Mascara has more to hold.
Maintain
Continue nightly. Results are held only with continued use, as with any lash treatment.
The ritual
One stroke, once a night.
The serum is applied to skin, not to the lashes. It goes where the lash meets the lid, on a clean, dry, oil-free surface, before anything else in the evening routine.
Cleanse and dry
Remove all makeup and oil. The lash line must be completely dry. Residue blocks the actives from reaching the root.
Draw the line
One pass of the wand along the upper lash line, at the root, as you would apply liner. Do not apply inside the eye or to the lower lashes.
Let it dry, then continue
Allow a minute. Follow with Definitive Eye Cream and the rest of the evening ritual once the serum has fully set.
In context
Three ways to treat a lash. One of them is skincare.
The category offers a drug in a cosmetic tube, or a conditioner that never reaches the root. Definitive Lash Serum is the third option, and the only one built to the standard of the rest of the AUTEUR line.
| Approach | Prostaglandin serums | Conditioning serums | AUTEUR Definitive Lash Serum |
|---|---|---|---|
| How it works | A synthetic hormone analog forces the growth phase to run longer | Coats the fiber. Little to no activity at the root | Peptides and a plant biotech active signal at the follicle. Amino acids and biotin condition the fiber |
| Actives | One drug-class molecule, sometimes with peptides added | Panthenol, oils, a vitamin or two | Four peptide complexes and an amino acid conditioning system. Five separate jobs |
| Known risks | Iris darkening, eyelid pigmentation, loss of fat around the eye, redness. Restricted in Canada and the EU | None, and little result | None of the prostaglandin effects. Fragrance-free, oil-free, hormone-free |
| Frequency | Nightly, then taper to avoid side effects | Twice daily | Once a night |
| Fits an eye ritual | Must be isolated from other actives | Sits on top of the routine | Applied first, dries, then Definitive Eye Cream |
Hold. Density. Length.
Once a night. Nothing you will regret in five years.
The eye ritual
Lash Serum first. Eye Cream after.
The Definitive Eye Cream addresses the skin around the eye. The Lash Serum addresses the hair that grows from it. Applied in that order, once the serum has dried, they complete the eye as a single evening step.
Questions
Before you begin.
Does it contain prostaglandins or any hormone?
No. The formula contains no prostaglandin analogs, no hormones and no progesterone. The actives are peptides, a turmeric-derived biotech extract, biotin, panthenol and amino acids.
How long until I see a change?
Most people notice less shedding within the first two weeks. First visible improvement in density typically appears after 14 to 28 days of nightly use. Length follows as new lashes clear the lid, usually by week eight. Results are maintained with continued use.
Can I use it with lash extensions or contact lenses?
Yes to both. Apply to a clean, dry lash line and allow the serum to dry fully. Remove contact lenses before application and wait a few minutes before reinserting. Extensions do not interfere with application at the root.
Can I use it on my brows?
The serum was developed for the upper lash line. Several of its actives are also used in brow treatments. Speak with your AUTEUR advisor before applying it to the brow.
What if I have sensitive eyes?
The formula is fragrance-free and oil-free, and the actives carry ocular tolerance data from their suppliers. It does not go inside the eye. If you have an eye condition or are pregnant or nursing, speak with your physician before starting any lash treatment.
How long does one tube last?
Used once nightly with a single pass along each upper lash line, one 5 ml tube carries you through the first full cycle of results. Replenish before it runs out so the routine is not interrupted.