Do lash primers do anything?

Quick answer

Yes. A lash primer gives mascara something to grip, so the color that follows lands with more visible volume, length and definition, and SeneGence makes its own. UnderSense® 3-in-1 Maximizing Lash Primer instantly boosts the look of lash length, volume and definition. It prepares a base for smoother, longer-lasting mascara wear, while peptide care nourishes and strengthens lashes. Beauty Book 2026 (p. 35).

By SeneGence · Alan Kante, publisher · Updated October 30, 2026

2 min read
Peptides

UnderSense® 3-in-1 Maximizing Lash Primer by SeneGence: A pale blue lash-primer tube with a gold cap. — A pale blue lash-primer tube with a gold cap.

How UnderSense -in- Maximizing Lash Primer builds and conditions lashes — UnderSense gives mascara a base to grip and conditions lashes with peptide care. UnderSense 3-in-1 Maximizing Lash Primer is a light-beige primer that gives mascara a base to grip and conditions lashes with Acetyl Tetrapeptide-3, Trifolium Pratense (Clover) Flower Extract, Biotinoyl Tripeptide-1 and Jojoba Esters.

What does UnderSense do for lashes?

UnderSense® 3-in-1 Maximizing Lash Primer is the base that goes on before mascara. Its light-beige tint means you see every coat as you place it, so placement is deliberate, and it makes mascara color look richer. Soft waxes keep each coat smooth and buildable instead of clumping, and the small wand reaches short lashes. Jojoba Esters condition, and the primer’s film stays flexible as it builds, coat on coat.

What is in UnderSense?

UnderSense pairs Acetyl Tetrapeptide-3 with Trifolium Pratense (Clover) Flower Extract and adds Biotinoyl Tripeptide-1 for healthier-, thicker-looking lashes over time. That peptide-and-clover pair has research of its own. For the full Butylene Glycol, Water, Dextran, Acetyl Tetrapeptide-3, and Trifolium Pratense (Clover) Flower Extract material, the manufacturer reports up to 27% lash-density improvement with a 93% responder rate at week 8 in a 17-woman split-eye study of a 2.5% material gel versus opposite-eye placebo, used morning and evening. See the lash and hair studies, the UnderSense formula or our peptide map.

How do you apply a lash primer?

Apply UnderSense to clean top and bottom lashes.
Add coats for more length and volume.
Let it dry fully; that dry-down is your cue for mascara.
Finish with any LashSense® mascara; over fully dry UnderSense, LashSense® FiberExtend Mascara adds even more volume and color.

UnderSense.

Benefits, formula & use

UnderSense® 3-in-1 Maximizing Lash Primer

Benefits: Choose UnderSense® 3-in-1 Maximizing Lash Primer to instantly add volume, length and definition before mascara while it nourishes and strengthens lashes.
Application: Apply UnderSense to top and bottom lashes, allowing it to fully dry. You may apply several coats for buildable volume and length. Finish with LashSense mascara for even more volume and amazing color.
Good For: UnderSense® 3-in-1 Maximizing Lash Primer suits maximizing mascara performance while supporting healthier-looking lashes.

SeneGence Beauty Book 2026, p. 35 · Current formula and directions: official SeneGence product page · View UnderSense® 3-in-1 Maximizing Lash Primer on SeneGence

UnderSense® 3-in-1 Maximizing Lash Primer

Choose UnderSense® 3-in-1 Maximizing Lash Primer to instantly add volume, length and definition before mascara while it nourishes and strengthens lashes.

UnderSense® 3-in-1 Maximizing Lash Primer suits maximizing mascara performance while supporting healthier-looking lashes.

How to use UnderSense® 3-in-1 Maximizing Lash Primer

Apply UnderSense to top and bottom lashes, allowing it to fully dry. You may apply several coats for buildable volume and length. Finish with LashSense mascara for even more volume and amazing color.

Read the ingredients

Water/Aqua/Eau Synthetic Beeswax Glycerin Stearic Acid Jojoba Esters Copernicia Cerifera (Carnauba) Wax Titanium Dioxide (CI 77891) Butylene Glycol Aminomethyl Propanol Acetyl Tetrapeptide-3 Trifolium Pratense (Clover) Flower Extract Acacia Senegal Gum Caprylyl Glycol Phenoxyethanol Hydroxyethylcellulose Potassium Sorbate Euphrasia Officinalis (Eyebright) Extract Dextran Ictasol Melia Azadirachta (Neem) Seed Oil Salix Alba (White Willow) Bark Extract Curcuma Longa (Turmeric) Rhizome Extract Maltodextrin Syringa Vulgaris (Lilac) Leaf Cell Culture Extract Panthenol Trifolium Pratense (Clover) Extract Vigna Radiata (Mung Bean) Seed Extract Sodium Benzoate Disodium Phosphate Nigella Sativa (Black Cumin) Seed Oil Pimpinella Anisum (Anise) Seed Extract Polysorbate 60 Tocopherol Oligopeptide-10 Biotinoyl Tripeptide-1 Sodium Phosphate Iron Oxide (CI 77492) Iron Oxide (CI 77491).).

How to choose & use Official product page Formula and sources

Study results at a glance

Acetyl Tetrapeptide-3 with Clover and Dextran — hair and lash studies8 results

Acetyl Tetrapeptide-3 with Clover and Dextran — hair and lash studies
Result	Kind of result	When it was measured
For the full Butylene Glycol, Water, Dextran, Acetyl Tetrapeptide-3, and Trifolium Pratense (Clover) Flower Extract material, the ingredient’s maker reports follicle elongation 58%, 51%, and 87% higher than untreated follicles at days 4, 7, and 11 in an ex vivo assay of 22 treated and 34 untreated follicles from one donor using 1% material.	Measured result	day 4; day 7; day 11
For exact Acetyl Tetrapeptide-3, the ingredient’s maker reports 47% greater elongation than untreated follicles at day 7 in an ex vivo assay of 15 peptide-treated, 27 minoxidil-reference, and 27 untreated follicles; its stated reference comparison belongs only to that assay.	Measured result	day 7
For the full Butylene Glycol, Water, Dextran, Acetyl Tetrapeptide-3, and Trifolium Pratense (Clover) Flower Extract material, the ingredient’s maker reports mean anagen density 9% higher, mean telogen density 42% lower, and anagen-to-telogen ratio 88% higher at day 90 in a 23-person baseline-controlled rinse-off scalp study using 1.5% material in shampoo and conditioner every two days.	Measured result	day 90
For the full Butylene Glycol, Water, Dextran, Acetyl Tetrapeptide-3, and Trifolium Pratense (Clover) Flower Extract material, the ingredient’s maker reports the two specified Cutibacterium acnes scalp-microbiome ratios 36% and 62% lower at day 90 in 21 people using the rinse-off regimen.	Measured result	day 90
For the full Butylene Glycol, Water, Dextran, Acetyl Tetrapeptide-3, and Trifolium Pratense (Clover) Flower Extract material, the ingredient’s maker reports a 15% favorable anagen-density delta, 52% favorable telogen-density delta, and 79-point between-group anagen-to-telogen-ratio delta after four months in a randomized 29-person leave-on scalp study using 5% material nightly.	Measured result	four months

Show 3 more results

Acetyl Tetrapeptide-3 with Clover and Dextran — hair and lash studies, more results
Result	Kind of result	When it was measured
For the full Butylene Glycol, Water, Dextran, Acetyl Tetrapeptide-3, and Trifolium Pratense (Clover) Flower Extract material, the ingredient’s maker reports up to 27% lash-density improvement with a 93% responder rate at week 8 in a 17-woman split-eye study of a 2.5% material gel versus opposite-eye placebo, used morning and evening.	Measured result	week 8
For the full Butylene Glycol, Water, Dextran, Acetyl Tetrapeptide-3, and Trifolium Pratense (Clover) Flower Extract material, the ingredient’s maker reports 45.5% more new lashes on the active side at week 8 while the placebo side recorded no new lashes in the same 17-woman split-eye study.	Measured result	week 8
For the full Butylene Glycol, Water, Dextran, Acetyl Tetrapeptide-3, and Trifolium Pratense (Clover) Flower Extract material, the ingredient’s maker reports lash length increased by up to 0.70 mm at week 4 in the same 17-woman split-eye study and puts the active-side improvement at three times placebo at week 4 and five times placebo at week 8.	Measured result	week 4; week 8

Who took part: Human studies included 29 leave-on participants, 23 rinse-off participants, 21 microbiome participants, and 17 split-eye lash participants
How it was evaluated: Randomized leave-on scalp study, baseline-controlled rinse-off scalp work, scalp-microbiome analysis, split-eye lash imaging, and ex vivo human-hair-follicle assays
Statistical context: Across distinct studies, the ingredient’s maker reports fuller-looking hair and lashes, scalp-microbiome changes, and follicle elongation.

See the full finding: Acetyl Tetrapeptide-3 with Clover and Dextran — hair and lash studies · Open the source document (PDF)

Full ingredient list

UnderSense® 3-in-1 Maximizing Lash PrimerIngredient guide

Official product reference checked September 18, 2026. View UnderSense® 3-in-1 Maximizing Lash Primer on SeneGence