skin pH values increase significantly faster following lactic acid application in patients with sensitive skin than in those without.3,4 Positive results on lactic acid sting tests have also been shown to correlate with self-reported skin sensitivity and with objective measures of stratum corneum function such as, transepidermal water loss.6 The goal of this study is to examine the relationship between subjective skin sensitivity and objectively measured skin sensitivity using the lactic acid sting test, and evaluate whether skin sensitivity varies according to Fitzpatrick skin type.
METHODS
Participants
100 participants took part in the study following informed consent. These patients were recruited on a volunteer basis from our dermatology clinic and waiting room. Exclusion criteria included a diagnosed facial skin disorder that would interfere with evaluation, a known allergy to lactic acid, the use of a topical retinoid or hydroxy acid within two weeks, and pregnant women. Participants were not remunerated for their participation in any way. Of the 100 participants, 70% were female and 30% were male. 57% were Fitzpatrick skin types 1–3 and 43% were Fitzpatrick skin types 4–6. All participants were over the age of 18.
Procedure
Patient skin type was assessed on the Fitzpatrick skin type scale. Scores range from 1–6, with scores of 1 indicating the palest skin tone with no inherent melanin pigmentation, and 6 indicating the darkest skin tone with a significant amount of melanin.8 Participants were then asked to report self-perceived skin sensitivity on a scale from 1 (none) to 5 (severe).
A single-blinded, lactic acid sting test was performed on the medial cheeks, where patients were randomized to receive room temperature 10% lactic acid on the left or right cheek with water applied to the contralateral cheek as a control using cotton tipped applicators. Static assessments of stinging were performed at 1 minute after application of test solution on the cheek using a visual analogue scale (VAS) (Appendix 1), on which participants were asked to indicate how much stinging they felt on a scale of 0 to 100. Solution was then rinsed off. The second solution was subsequently applied to the other cheek, after which the second stinging assessment was performed, using the same methods.
100 participants took part in the study following informed consent. These patients were recruited on a volunteer basis from our dermatology clinic and waiting room. Exclusion criteria included a diagnosed facial skin disorder that would interfere with evaluation, a known allergy to lactic acid, the use of a topical retinoid or hydroxy acid within two weeks, and pregnant women. Participants were not remunerated for their participation in any way. Of the 100 participants, 70% were female and 30% were male. 57% were Fitzpatrick skin types 1–3 and 43% were Fitzpatrick skin types 4–6. All participants were over the age of 18.
Procedure
Patient skin type was assessed on the Fitzpatrick skin type scale. Scores range from 1–6, with scores of 1 indicating the palest skin tone with no inherent melanin pigmentation, and 6 indicating the darkest skin tone with a significant amount of melanin.8 Participants were then asked to report self-perceived skin sensitivity on a scale from 1 (none) to 5 (severe).
A single-blinded, lactic acid sting test was performed on the medial cheeks, where patients were randomized to receive room temperature 10% lactic acid on the left or right cheek with water applied to the contralateral cheek as a control using cotton tipped applicators. Static assessments of stinging were performed at 1 minute after application of test solution on the cheek using a visual analogue scale (VAS) (Appendix 1), on which participants were asked to indicate how much stinging they felt on a scale of 0 to 100. Solution was then rinsed off. The second solution was subsequently applied to the other cheek, after which the second stinging assessment was performed, using the same methods.
RESULTS
Of the 100 study participants, 62% reported having sensitive skin (defined as self-reported scores of 3–5), while 38% reported none or minimal sensitivity (self-reported scores of 1–2). Significantly more patients with Fitzpatrick skin types 1–3 reported sensitive skin, as compared to those with skin types 4–6 (73.6% vs 46.5%; P=0.006). Overall, on lactic acid assay, 38% of all participants demonstrated skin sensitivity. We defined objectivity sensitivity as stinging to the acid above the mean stinging of all participants to water. When stratified by skin type, a numerically higher percentage of subjects with Fitzpatrick skin types 1–3 experienced objective sensitivity to the lactic acid compared to subjects with skin types 4–6, although this was just under the threshold for statistical significance (45.6% vs 27.9; P=0.058). Additionally, those who had higher perceived sensitivity were more likely to exhibit objective sensitivity (P<0.01). No statistical differences were observed in perceived or objective sensitivity when stratified by gender or ethnicity.
DISCUSSION
This study aimed to examine the relationship between skin sensitivity and skin type. We specifically looked at the difference in perceived sensitivity between across skin types as well as a correlation between perceived and objective skin sensitivity. We found that perceived skin sensitivity was more common in lighter skin types (Fitzpatrick 1–3) as compared to darker skin types (4–6). Furthermore, we found that patients’ prior perceptions of their own skin sensitivity reflected what they reported on lactic acid testing in the study. In clinical practice, this implies that simply asking patients about their perceived skin sensitivity may be useful in selecting appropriate therapeutics and treatment regimens. This approach optimizes patient outcomes and makes the care process inherently more efficient.
The results also showed that more patients with lighter skin tones experienced stinging following lactic acid application as compared to those with darker skin tones, although not statistically significant. Given our small sample size, it is unclear whether this difference is real, and larger studies will be needed for further evaluation. Regardless, it is important to note that both subjective and objective skin sensitivity occurs across all skin types, and we cannot make assumptions about sensitivity based solely on Fitzpatrick skin type. Moreover, this study helps dispel myths that women’s skin is more sensitive than men’s and that sensitivity is more common in specific ethnic groups.
Our study is limited by the small sample size of 100 patients, primarily comprised of female patients, which may impact responses. Despite these limitations, this study demonstrates that skin sensitivity is common, and while it may occur more often in light skinned patients, it should be considered in patients of all skin types.
The results also showed that more patients with lighter skin tones experienced stinging following lactic acid application as compared to those with darker skin tones, although not statistically significant. Given our small sample size, it is unclear whether this difference is real, and larger studies will be needed for further evaluation. Regardless, it is important to note that both subjective and objective skin sensitivity occurs across all skin types, and we cannot make assumptions about sensitivity based solely on Fitzpatrick skin type. Moreover, this study helps dispel myths that women’s skin is more sensitive than men’s and that sensitivity is more common in specific ethnic groups.
Our study is limited by the small sample size of 100 patients, primarily comprised of female patients, which may impact responses. Despite these limitations, this study demonstrates that skin sensitivity is common, and while it may occur more often in light skinned patients, it should be considered in patients of all skin types.
DISCLOSURES
Dr. Joshua Zeichner is a consultant for Abbvie, Dermira, Galderma, Johnson and Johnson, L’Oreal, Menlo Therapeutics, Ortho Dermatologics, Pfizer, Procter and Gamble, Regeneron, Sanofi-Genzyme, Sun Pharma, and Unilever.
Celina Dubin has no conflict of interests to declare. Drs Kimmel, Hashim, and Nia have no conflicts of interest to declare.
Celina Dubin has no conflict of interests to declare. Drs Kimmel, Hashim, and Nia have no conflicts of interest to declare.
