Biometric Evaluation of Baumann Skin Typing

With the increasing demand for personalized skincare, accurate identification of individual skin types has become essential. The Baumann skin type (BST) classification system is widely used in clinical and commercial settings, yet lacks sufficient biometric validation. This study aims to evaluate the correlation between BST categories and objective skin biophysical parameters.

Seventy-one healthy volunteers participated in the study. Skin parameters including stratum corneum hydration, transepidermal water loss (TEWL), melanin index, sebum levels, elasticity, and pH were measured using the MPA 580 system. Skin thickness and echodensity of the epidermis and dermis were assessed via high-frequency ultrasound (HFU), while depth, area, and volume of the nasolabial folds were analyzed using VisioFace CSI software. Each participant completed the BST questionnaire, and correlations between BST scores and measured skin parameters were assessed using Pearson's correlation coefficient.

The oily vs. dry score was correlated with hydration (r = 0.08, p = 0.507), TEWL (r = -0.065, p = 0.591), and sebum (r = 0.299, p = 0.011). The sensitive vs.resistant score correlated with TEWL (r = 0.388, p = 0.001) and pH (r =  0.445, p < 0.001). The pigmented vs. non-pigmented score correlated with melanin index (r =  0.280, p = 0.018). The wrinkle vs. tight score was correlated with skin firmness (R0; r = 0.495, p< 0.001), total skin elasticity (R2; r = -0.318, p = 0.007), dermal thickness (r = -0.242, p = 0.042), dermal density (r = -0.189, p = 0.115), epidermal thickness (r = -0.128, p = 0.288), nasolabial fold volume (r = 0.138, p = 0.250), surface (r = 0.150, p = 0.213), and depth (r = 0.048, p = 0.690).

The oily vs. dry (O/D) score showed a poor but significant correlation with sebum, while hydration and TEWL were not significant. The pigmented vs. non-pigmented (P/NP) score demonstrated a poor but significant correlation with the melanin index. The sensitive vs. resistant (S/R) score showed fair and significant correlations with TEWL and pH. The wrinkle-tight (W/T) score showed fair and statistically significant correlations with elasticity parameters (R0 and R2), while correlations with nasolabial fold parameters, dermal density, and epidermal thickness were not significant; dermal thickness showed a poor but statistically significant correlation.