Half of volunteers in one study called their skin sensitive, yet two-thirds reacted to a lactic acid sting test, and the groups only partly overlapped. Here is what each tool measures and how to shop with that in mind.
· 5 min read
Plenty of people say their skin is sensitive. Fewer know that researchers have two common ways of checking, a questionnaire and a lab stinging test, and that the two often give different answers about the same person. This matters when you are deciding how cautiously to introduce a new product, because 'sensitive' can mean very different things depending on how it was measured.
Sensitive skin is described in the research literature as a cluster of unpleasant sensations, such as stinging, burning, itching and tightness, often with little that is visible. Because there is no single reading that captures a sensation, studies lean on two instruments. The first is a self-assessment questionnaire, where people rate how their skin reacts to triggers such as weather, soaps or cosmetics. The second is the lactic acid sting test (LAST), where a lactic acid solution is applied to the nasolabial fold under supervision and the person scores the stinging they feel over several minutes.
Both are subjective in the end, since the LAST also relies on the volunteer reporting a sensation. What differs is what each one captures: the questionnaire reflects everyday history and expectations, while the LAST measures a reaction to one standardized challenge on one day.
A 2021 cross-sectional study of 209 healthy Chinese women applied both methods. By questionnaire, 50.2% had sensitive skin; by LAST, 66.0% did. Women who rated themselves as sensitive had a slightly higher LAST-positive rate, but the overlap was far from complete. A 2019 study of 292 women who already believed their skin was sensitive found that some were still negative on the LAST, which the authors described as a known limitation of the test.
The practical reading: if you feel sensitive but would not 'sting' in a lab, that does not make your experience imaginary. It may mean your reactivity shows up as something the standard challenge does not provoke.
The 2019 study broke sensitivity into symptoms. LAST scores tracked the questionnaire scores for stinging, itching, tightness and scaling, but not for burning or redness. So a person whose main complaint is flushing or burning may be underrepresented by a test built around stinging.
The same study linked higher LAST scores to lower stratum corneum hydration and higher transepidermal water loss (TEWL), a measure of how readily water leaves the skin. That fits a common-sense picture in which a drier, less comfortable surface tends to sting more readily. The 2021 study added that the LAST-positive group had higher TEWL and redness readings than the LAST-negative group. Correlation is not cause, so the studies do not show that a weaker barrier is the reason, only that the two travel together.
A 2022 study tested a self-assessment questionnaire against the LAST, enrolling 102 LAST-positive volunteers and 60 LAST-negative controls. It asked people to rate their own sensitivity from 0 to 10 and then to answer ten items, each naming a specific possible trigger. Positive volunteers scored significantly higher, and the authors set a cutoff to separate the groups. The takeaway is that specific questions about real-world triggers appear more informative than a simple 'do you have sensitive skin?'
A 2024 study took a similar route with a four-item questionnaire scored 0 to 15. Its scores matched trained assessors' sensitive or not-sensitive classification 92.7% of the time in 183 people, which suggests short, well-built questions can be quite consistent. Note that this work was run by a team evaluating a cosmetic cream and used imaging, so it is best read as a methods paper rather than proof of any product effect.
Use the findings to shape your approach rather than to label yourself:
For any new product, patch test on the inner forearm or behind the ear for several days, then use it on one small area of the face. Add one new product at a time, wait at least a week between additions, and keep the rest of the routine boring: a gentle cleanser, a plain moisturizer and a daily broad-spectrum sunscreen. If you notice persistent stinging, redness or swelling, stop and talk to your doctor.
Roughly half of volunteers in one study called themselves sensitive, while two-thirds reacted to the sting test, and the two groups only partly overlapped. Neither tool is the whole truth. Judge a routine by your own repeatable reactions, introduce changes slowly, and read questionnaires and lab tests as two partial views of the same experience.
Rituelle reads your skin over time and adapts your routine to it.
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