OBJECTIVE: Pathogenic factors that reduce corneal biomechanical properties (CBPs) remain unclear. This study aimed to retrospectively analyze the effect of allergic predisposition on CBPs in normal corneas. DESIGN: Retrospective study. METHODS: Patients with atopic dermatitis (8 eyes), allergic conjunctivitis (18 eyes), vernal conjunctivitis (5 eyes), and atopic keratoconjunctivitis (14 eyes) in their 10s-30s who visited the Juntendo University Hospital were considered to have an allergic predisposition (+). Additionally, 32 eyes were included in the healthy control group without allergic predisposition (-). CBP parameters (Corvis Biomechanical Index, deformation amplitude [DA], peak distance, A1 velocity, and A2 velocity [A2V]) were assessed using Corvis ST (Oculus, Wetzlar, Germany) in all patients. The relationship between the CBP parameters and allergic predisposition was evaluated using multiple linear regression analysis with generalized estimating equations. RESULTS: Corneal shape analysis using CASIA (Tomey Corp., Nagoya, Japan) confirmed that no complications associated with keratoconus were present. Multivariate analysis revealed that an allergic predisposition (+) had a strong influence on A2V ( CONCLUSIONS: Allergic predisposition may affect CBP parameters in normal corneas, suggesting that A2V may be an early marker of keratoconus onset.