How we test and rank lash serums
A ranking is only as trustworthy as its rubric. Here is ours — the protocol, the weights, and the rules that keep affiliate revenue away from the scores.
The 12-week protocol
Every serum is used exactly as the brand instructs (usually one swipe along the upper lash line nightly on clean, dry skin) for 12 consecutive weeks. We chose 12 weeks because a full lash cycle runs 6–10 weeks; anything shorter measures conditioning, not growth.
Baseline
Macro photographs at week 0 under fixed lighting, distance and camera settings; lash length measured at three points per eye.
Weeks 4, 8, 12
Re-photographed under identical conditions. Testers log irritation, redness, dryness, lid darkening and any change in eye appearance daily.
Ingredient audit
Full INCI review against prostaglandin-analog structures, hormone-like actives, fragrance, essential oils and known sensitizers. Cross-checked with Health Canada's Hotlist and FDA warning-letter database.
Scoring & publication
Sub-scores are combined using fixed weights; results are published with pros, cons and a plain-English verdict. Re-run quarterly or when a formula changes.
The four pillars and their weights
| Pillar | Weight | What we measure |
|---|---|---|
| Efficacy | 35% | Measured length and density change at 12 weeks; time to first visible change; consistency across testers. |
| Safety | 30% | Ingredient audit, tester-reported irritation, published adverse-event data, regulatory status, third-party testing (ophthalmological/dermatological). |
| Value | 20% | Cost per ml, months of use per bottle, results relative to price. |
| Formula quality | 15% | INCI transparency, supporting ingredients, applicator design, stability, vegan/cruelty-free status. |
An overall score of 9+ means a serum performed well on every pillar. Scores between 7 and 8 usually mean a serum works but makes a significant trade-off — most often safety for speed.
Independence rules
- We buy every product at retail. We do not accept free product for ranked reviews.
- Affiliate links are added after scoring and never change position. A serum with no affiliate program is ranked exactly the same way.
- Brands cannot pay to be included, excluded or moved. Sponsored content, if ever published, is labeled and never appears in rankings.
- Any correction is logged with a date on the page it affects.
Limitations
Our tester group is small compared with a clinical trial, and lash response is individual. Our scores are a well-controlled consumer test, not a medical study. Where clinical data exists (Latisse), we say so and weight it.
Questions about our process? Email [email protected]. Read our editorial policy and affiliate disclosure.