Thermographic Quantification of Skin Prick Test Responses in Children: The Caloric Allergy Index

BACKGROUND: Skin prick tests(SPTs) are widely used diagnostic tests for evaluating type I hypersensitivity and are interpreted based on human-measured wheal diameters. However, their diagnostic value may be limited by variability in application, measurement, and interpretation due to human dependency. Medical thermography offers a non-invasive, objective, and quantitative method to assess local inflammatory responses. This study aimed to evaluate the feasibility and agreement of thermographic imaging for reading pediatric SPTs and to explore its potential role in supporting a more objective and standardized interpretation. MATERIALS AND METHODS: In this cross-sectional observational study, SPTs were performed on the upper backs of children aged 5-18 using a standardized aeroallergen panel, along with histamine and saline controls. Thermal images were captured at 0, 2, 5, 10, and 15 min using a mobile thermal camera. The Caloric Allergy Index(CAI) was established to quantify allergen-induced skin warming relative to positive and negative controls. RESULTS: Data from 63 pediatric patients were analyzed. Cohen's Kappa scores ranged from 0.432 to 0.838, indicating moderate to almost perfect agreement between CAI values and conventional wheal measurements. Allergens including grass mix(κ = 0.838) and C. dactylis(κ = 0.833) showed the highest agreement, followed by D. pteronyssinus(κ = 0.753) and D. farinae(κ = 0.672). Moderate agreement was observed for tree mix, cat, and dog epithelium. Positive test sites exhibited continuous warming, typically became statistically discernible in 2-5 min, while negative sites showed minimal change. CONCLUSION: This study introduces a thermographic parameter with overall agreement to conventional SPT readings, supporting the feasibility of thermography as a complementary objective approach in pediatric SPT interpretation.