Sensory Reactivity Tests
Irritant Reactivity Tests
Dermal Function Tests
To evaluate cutaneous neurosensory response to the application of different chemical substances, or physical stimuli
To assess objective signs of skin irritation after the application of SLS or other known irritants
To measure structural or physiological cutaneous changes after the application of topical irritants
• Self-assessment questionnaires
• Stinging test: 10% lactic acid (or capsaicin, ethanol, menthol, benzoic acid)
• Thermal sensation test (QST)
• Evaluation of itching response
• Washing and exaggerated immersion test
Assessment of cutaneous irritation by the following:
• Colorimetry (visual erythema)
• Laser Doppler velocimetry (nicotinate test)
• Electrical capacitance
• Corneometry (skin hydration)
• TEWL (basal or dynamic desorption curves)
• Cutaneous pH
• Epidermal thickness (measured by US, OM, or CM)
• Skin penetrability (measured by UV light)
Fast and easy to perform Subjective, intraindividual variability, and lack of predictive value
Objective and noninvasive Indirect measurement and specialized complex tools
Quantitative and accurate Time consuming, specialized, and expensive
Source: Primavera, G., and Beradesca, E., Int J Cosmet Sci, 27, 1–10, 2005; Piel, 28, Rodrigues-Barata, R., and Conde Salazar-Gómez, L., Sensitive skin, 520–530, Copyright (2013), with permission from Elsevier; Escalas-Taberner, J., González-Guerra, E., and Guerra-Tapia, A., Actas Dermosifiliogr, 102, 563–571, 2011.
Note: CM: confocal microscopy; OM: optical microscopy; QST: quantitative sensory test; US: ultrasonography.
To evaluate and quantify the severity of sensitive skin objectively, reproducible and noninvasive tests are absolutely necessary. According to Farage et al. (22,23), testing methods can be divided into three main groups depending on the biophysical factor assessed: those that investigate neurosensory response (sensory reactivity tests), those that evaluate visible cutaneous signs of irritation (irritant reactivity tests), and those that measure structural and physiological parameters of the skin as a consequence of the irritant effect (dermal function tests) (24). Table 8.1 represents an overview of the currently available testing methods.
Sensory Reactivity Tests
Because almost half of patients with sensitive skin report uncomfortable symptoms without accompanying visible signs of inflammation, new tools of sensory testing have been increasingly utilized to provide definite information (13).
These methods evaluate cutaneous neurosensory response to the application of different chemical substances or other physical stimuli (7). Of them, the stinging test of Frosch and Kligman (25), which consists of the application of 0.5 mL of 10% lactic acid to the nasolabial fold with subsequent assessment of the severity of the subjective symptoms, has traditionally been considered to be the most suitable, fast, and easy to perform (26). However, nasolabial stinging seems to be a poor predictor of general skin sensitivity (27). Marriott et al. (27