Redness and itching at the corners of the mouth may be caused by keratitis, perioral dermatitis, perioral eczema and other factors. 1. Keratitis: It may be related to bacterial or fungal infections, trauma and other factors that can lead to infections at the corners of the mouth, which can lead to redness at the corners of the mouth, accompanied by itching, pain and other symptoms. 2. Perioral dermatitis: it may be related to external stimuli, such as the use of fluoride toothpaste or cosmetics, etc., which can lead to the appearance of red pimples at the corners of the mouth, perinasal area, periorbital area, etc., accompanied by itching, burning sensation and other symptoms. 3. Perioral eczema: it may be related to heredity, allergy, habits and other factors, which can lead to small red blisters at the corners of the mouth, accompanied by itching, erosion, rough skin and other symptoms. Redness and itching at the corners of the mouth may have other causes, and it is recommended to go to the hospital in time to identify the causes and treat the symptoms.