Red patches on the face without itching or pain may be the manifestation of systemic lupus erythematosus (SLE), and there may be discoid lupus erythematosus (DLE) or dermatomyositis, which need to be analyzed specifically. 1. Systemic lupus erythematosus: the cause of the disease is relatively complex, fever, arthralgia and facial butterfly-shaped erythema are the most common early symptoms of the disease, typical lesions for the cheeks and the bridge of the nose edematous butterfly-shaped erythema, which is often aggravated by sun exposure, and there are no self-awareness of symptoms at the lesions. 2. Discoid lupus erythematosus: This disease is closely related to ultraviolet radiation, with a chronic course and good prognosis. Typical lesions are flat or slightly elevated discoidal erythema with adherent scales or plaques, and the center of the lesion gradually becomes atrophic and hypopigmented, while the surrounding area is hyperpigmented. The lesions often involve the face, without conscious symptoms. 3. Dermatomyositis: Dermatomyositis is a kind of autoimmune connective tissue disease that involves the skin and the transverse striated muscle, with subacute and chronic onset. Edematous purplish-red patches centered on the upper eyelids of both eyes, which can involve the cheeks and scalp, are the typical lesions of this disease. There are more reasons for red patches on the face that do not itch or hurt, and it is important to go to the hospital in time and standardize the treatment.