Multiple chemical sensitivity (MCS) - a guide for dermatologists on how to manage affected individuals

Does sensitive skin lie in epidermal barrier impairment or abnormalities? Results from an observational study assessing biophysical parameters

BACKGROUND

The pathophysiology of sensitive skin is largely unknown and no univocal data on the role of the epidermal barrier impairment have been identified. The aim of this study was to assess whether subjects with or without sensitive skin differ for some biophysical skin parameters, which reflect skin barrier integrity or skin hyperactivity.

METHODS

This observational, cross-sectional study included adult volunteers not affected with chronic inflammatory skin diseases who attended the Unit of Dermatology and the Center of Cosmetology of the University of Ferrara, Ferrara, Italy, between March 2021 and November 2022. All subjects, subdivided into those with or without sensitive skin, based on either Lactic Acid Stinging Test (LAST) result or a questionnaire-based skin sensitivity score ≥4, were tested for transepidermal water loss (TEWL), skin elasticity and hydrations and dermographism.

RESULTS

One hundred and eighty-seven subjects were included. No significant differences in terms of TEWL, elasticity and hydration levels were recorded between subjects with sensitive skin and those without, subdivided according to both the LAST result and the questionnaire score. Dermographism was elicited more in subjects with sensitive skin than in the others, although without statistical significance.

CONCLUSIONS

The study failed to find significant biophysical differences between sensitive and non-sensitive skin. Therefore, the role of skin barrier impairment does not appear to be a necessary condition in determining an abnormal skin sensitivity to potentially unpleasant and irritating stimuli. These findings indirectly support the relevance of a peripheral sensory neural hyperactivity in the pathophysiology of sensitive skin.

Results from an extended study on the reliability of a questionnaire for the diagnosis of sensitive skin: Confirmations and improvements

OBJECTIVE

A recently proposed self-assessment questionnaire aimed at diagnosing sensitive skin provided promising results in a relatively small population. The main objectives were: (i) to assess the reliability of the aforementioned questionnaire in a larger population and verify the cut-off score previously found to predict skin sensitivity (defined as positivity to LAST, lactic acid stinging test) and (ii) to define a formula that yields the probability of a positive LAST result.

METHODS

Adult volunteers were included in this observational, cross-sectional, extended study. Both LAST-positive subjects, who were considered as having sensitive skin ('patients') and negative ones ('controls') completed the questionnaire, which concerned sensitivity to possible triggers of unpleasant skin sensations in real life. A cumulative score (questionnaire-based skin sensitivity score, 0-10) was calculated from the sum of all items.

RESULTS

Three hundred and sixty-four subjects were enrolled, 214 patients and 150 controls. The mean questionnaire-based skin sensitivity score was significantly higher among patients than controls. Using two different methods, cut-off values of 4 and 5 were defined for the identification of LAST-positive subjects, with 76.6% and 72.8% accuracy, respectively. Scores below 4 or above 5 showed a high (80% or better) negative or positive predictive value, respectively. The coefficients found that in multivariate analysis for each questionnaire item, gender and age allowed us to calculate the probability of LAST positivity with higher precision taking into account the 'relative weight' of each factor.

CONCLUSION

With small variations in the results, the self-assessment questionnaire confirmed its reliability for diagnosing sensitive skin in clinical practice.

Proposal of a self-assessment questionnaire for the diagnosis of sensitive skin

Background

Sensitive skin is very common and distressing. Its diagnosis may be difficult with the tools/methods available at the moment.

Aims

To assess the reliability of a self‐assessment questionnaire for the diagnosis of sensitive skin, using the results of lactic acid stinging test (LAST) as a reference for the identification of subjects suffering from this condition. A further objective was to identify the questionnaire cutoff score that better discriminates between subjects with or without sensitive skin.

Patients/methods

Among the adult volunteers included in this observational, cross‐sectional study, both LAST‐positive subjects, who were considered as having sensitive skin (“patients”), and negative ones (“controls”) completed the questionnaire. It consisted of a part for self‐assessing and quantifying (0–10) sensitive skin and another one that included 10 items, each referring to a specific, potentially triggering stimulus. A cumulative score (questionnaire‐based skin sensitivity score, 0–10) was calculated from the sum of all items considered capable of triggering unpleasant skin sensations in real‐life experience.

Results

One hundred and sixty‐two subjects were enrolled, 102 patients and 60 controls; 98 subjects thought they had sensitive skin. The mean questionnaire‐based skin sensitivity score was significantly higher among patients than controls and correlated with skin sensitivity self‐assessments. A cutoff value of 3 was set for the identification of LAST‐positive subjects, with 79% accuracy.

Conclusions

The study self‐assessment questionnaire seems to be a reliable tool for diagnosing sensitive skin in clinical practice. These results led us to identify a numerical cutoff for detecting propensity to experience sensitive skin.