We explore phytochemicals that inhibit AHR activation in keratinocytes. Cinnamaldehyde contained in Cinnamomum cassia extract inhibits AHR activation. Cinnamaldehyde activates the NRF2/HO1 pathway and alleviates ROS production. The AHR and the NRF2/HO1 pathways are independently modulated by cinnamaldehyde. Formulae containing Cinnamomum cassia extract inhibits AHR activation.