Developmental toxicity assessment of Allura Red AC in SD rats: A focus on skeletal ossification

Allura Red AC, a widely used synthetic azo dye in food and beverages, lacks comprehensive data on developmental toxicity across exposure levels-prompting this evaluation of developmental toxicity in Sprague-Dawley (SD) rats per standardized guidelines. Fifty pregnant rats were randomly assigned to oral gavage treatments: Allura Red AC at 40, 200, or 1000 mg/kg/day, distilled water (negative control), or 300 mg/kg aspirin (positive control) from gestation day (GD) 6-15, a critical window for organogenesis. Maternal and fetal parameters were assessed on GD 20.The positive control group showed significant embryotoxicity, validating the test system's sensitivity. Notably, Allura Red AC at ≥ 40 mg/kg caused a statistically significant reduction in fetal posterior fontanel width vs. the negative control-hinting at effects on cranial bone ossification. No adverse changes emerged in maternal reproductive metrics (e.g., weight gain, implantation sites) or key fetal indicators (viability, body size, sex ratio, external/visceral/skeletal malformations). Under this study's conditions, Allura Red AC induced no overall adverse developmental toxicity, and no teratogenic structural malformations but may alter specific cranial ossification patterns at doses ≥ 40 mg/kg. However, this finding cannot prove that Allura Red AC fails to change cranial ossification patterns at doses below 40 mg/kg.