The causes of erythema on the body without pain and itching are considered as follows: 1. Systemic lupus erythematosus: mostly seen in women of childbearing age, it is an autoimmune system disease that can involve multiple organs throughout the body. Patients with SLE can develop erythema in the facial area as well as other parts of the body, and it is not accompanied by pain or itching, and it will worsen after sun exposure, especially in the facial area where butterfly-shaped erythema has appeared. This is a kind of congenital capillary malformation, which mainly appears on the face, neck and other parts of the body as light red red spots of different sizes, without pain and itching, and can be treated by laser and photodynamic therapy. Therefore, for erythema on the body that is not painful or itchy, laser treatment and photodynamic therapy can be applied. Therefore, for erythema on the body without pain or itching, patients need to go to a regular hospital and under the guidance of a dermatologist to conduct the corresponding laboratory tests to confirm the diagnosis and to guide the clinical treatment.