Itch is an unpleasant sensation that evokes the urge to scratch and can lead to reduced concentration, sleep disturbances, and decreased quality of life. Conventional assessment methods, such as the visual analog scale (VAS) and verbal rating scale (VRS), are widely used to evaluate itch intensity; however, these methods are subjective and may be influenced by the participants’ perceptions or evaluators’ interpretations. This study aimed to examine the feasibility of objectively quantifying itch intensity using transcutaneous electrical stimulation. In Experiments 1 and 2, two types of itch perception thresholds, the initial itch perception threshold (IPT) and the maximum itch perception threshold (IMT), were measured and compared with each participant’s current perception threshold (CPT). Both IPT and IMT showed strong correlations (r or ρ ≥ 0.81) and positive regression relationships (R² ≥ 0.68) with CPT values. In addition, subjective evaluations revealed a strong positive correlation between VAS and VRS scores (ρ ≥ 0.61). In Experiment 3, a 20-Hz square wave electrical stimulus at a 50% duty cycle was applied while incrementally increasing the stimulation intensity from 1.2 to 2.0 times each participant’s IPT. VAS scores increased significantly with increasing stimulation intensity, and statistical analysis revealed a significant main effect of stimulation level (p < 0.001). In Experiment 4, itch was induced by topical application of yam (calcium oxalate) to the skin. Itch intensity was quantified using the proposed Itch Index calculated from the ratio of IPT to CPT, as well as the VAS. A significant positive correlation was observed between the Itch Index and VAS score (r = 0.77, p = 0.01), supporting the validity of the proposed evaluation method. In contrast, no clear correlation between the Itch Index and VAS score was observed in Experiment 2, which may be attributable to inter-individual differences in sensitivity to electrically induced itch. Further investigation is required to clarify this relationship. Overall, the Itch Index based on transcutaneous electrical stimulation represents a promising approach for objective quantification of itch. This method complements conventional subjective assessment tools and may contribute to improved evaluation of pruritic symptoms.