Three things get called “cooling”
- Thermal effect. A measured change in skin surface temperature, in degrees, over time. Objective and repeatable if the room is controlled.
- Sensory intensity. What a panellist reports on a labelled scale. This is what the consumer experiences, and it does not track temperature linearly.
- Duration. How long either of the above stays above a defined threshold. The threshold is a choice, and it should be stated.
An eight-hour claim can therefore mean: the mean temperature drop over eight hours, the time until the sensory score returned to baseline, or the time until the effect fell below some fraction of peak. All three are legitimate. Only one of them is being quoted, and the pack never says which.
Method 1 — thermal measurement
Either a thermocouple/thermistor probe taped to the site, or infrared thermography of a defined region. What makes the result usable:
- A climate-controlled room, typically 20–22 °C and 45–55% relative humidity.
- Twenty minutes of acclimatisation before baseline, and the same site on every subject.
- A baseline taken immediately before application, and the base without active as a control.
- Fixed application volume or weight per area — otherwise you are measuring how much product was used.
- Mean over the full window reported alongside peak, not instead of it.
Thermography is fast and photogenic and easy to misuse: emissivity, distance, angle and ambient reflections all move the number. A probe is less impressive in a brochure and harder to argue with.
Method 2 — sensory panel
A trained panel scoring intensity on a 0–10 or 0–100 scale at fixed time points, ideally with time–intensity recording rather than a single end score. What matters:
- Descriptors scored separately: cool, fresh, burn, sting, tingle, after-feel. A high burn score is not a high cooling score, but it is often reported as one.
- Blind coding and randomised application order, or the panel will find what the moderator expects.
- Enough subjects to see a difference: small panels reliably detect large effects and reliably miss small ones.
- A no-treatment control, because the room itself cools the skin.
Method 3 — release and retention
When the question is “why did it fade”, the answer is often not on the skin at all. Franz-cell release across a membrane, or headspace GC to measure how much sensate leaves the product during storage, explains a fade that a panel can only describe.
What our own number means
The comparison on the technology page is an eight-hour mean temperature drop on a cooling patch, five patches per cell, three agents at two use levels. It is a thermal measurement on the substrate the study was designed for.
The interesting result is not the absolute value — it is that two of the three agents lost performance when the dose doubled, while the ester did not. That is a formulation finding, and it is testable by anyone with a probe and a week.
The seven things to ask before you repeat a supplier's figure
- Which measurement — thermal, sensory or release?
- Mean or peak, and over what window?
- How many subjects or patches per cell?
- What was the control — untreated, or base without active?
- What substrate — patch, skin, membrane, shampoo?
- Internal study or third party, and is the report available?
- Was the difference statistically tested, or is it a ranking of two means?
Answer the first four and you have a number you can put in a claim substantiation file.
How to substantiate the claim
In the EU, cosmetic claims must be substantiated; in the US, the FTC applies a similar evidence standard to advertising. A defined duration plus a method is what makes a cooling claim hold up — “measured mean temperature reduction of X °C over eight hours on a cooling patch, n=5” is defensible, and it is also more persuasive to a formulator than an adjective.
This article describes test methods, not a claim for any CITRAVION product. Method details for our internal study are released under NDA.