This article summarises Professor Xiong Lei's experience in treating recurrent oral ulcers in children by applying the theory of fire and toxicity in sores and ulcers. Based on the theory of fire and toxicity in ulcers, professor Xiong Lei believes that recurrent oral ulcers in children are mostly caused by fire and toxicity, which are related to the five viscera, and there is a difference between cold and heat, and there is a difference between real and imaginary. Based on the theory of Chinese medicine organs and meridians, this paper explains professor Xiong Lei's experience in applying the "fire and toxin theory of sores" to treat children's recurrent oral ulcers from the organs, and explores the specific application of aromatic herbs in this disease. A case is attached for verification.