Background: Botulinum toxin type A (BoNT-A) is widely used for cosmetic wrinkle reduction, but injection-related pain varies among patients. Given that factors such as sex, BMI, handedness, and prior injection experience may influence pain perception, this study aimed to investigate the asymmetry of pain perception in botulinum toxin injection.
Methods: This cross-sectional study was conducted in the surgical department of 5 Azar Hospital and a private clinic in Gorgan, Iran. A total of 84 eligible subjects (68 females and 16 males) receiving botulinum toxin type A injection in the forehead were enrolled. Pain severity was assessed five minutes post-injection using the Visual Analogue Scale (VAS, 0–10). Each participant provided a separate VAS score for the left and right sides of the forehead, resulting in paired measurements for analysis. Statistical analyses, including paired t-tests, Pearson correlation, and linear regression model, were employed to examine the effects of variables such as gender, age, BMI, and handedness. A p-value of less than 0.05 was considered statistically significant.
Results: This study included a total of 84 participants, predominantly female (81%). A paired analysis revealed that pain was generally higher on the left side, with females reporting significantly greater discomfort than males (P = 0.037). Prior injection experience was associated with reduced pain asymmetry (R = –0.227, P = 0.038). Multiple regression analysis identified sex (P = 0.025, β = 0.218) and BMI (P = 0.012, β = 0.293) as significant predictors of pain difference.
Conclusion: Adopting individualized injection strategies that consider these patient-specific factors (such as sex and BMI) is crucial for enhancing comfort and satisfaction during the procedure.
