Erythematous papules can be hives, measles, eczema, lupus erythematosus and other diseases. 1. Hives: In case of urticaria, this is when the skin becomes irritated due to an allergic reaction, which leads to dilation of the blood vessels and swelling of the tissues of the skin, and therefore erythematous papules appear. 2. Measles: Because of measles virus infection, these viruses can damage the skin, resulting in redness and swelling of the skin, also appear erythematous papules. 3. Eczema: In the case of eczema, the skin is easily damaged due to the stimulation of inflammatory factors, which triggers the appearance of red rashes. 4. Lupus erythematosus: when the patient’s immune function is dysfunctional, the immune system can attack normal skin tissues, triggering damage to the skin and the appearance of red rashes. The phenomenon of erythema papulosum may also be caused by other diseases, it is recommended to go to the hospital in time for examination, to clarify the cause of the disease under the guidance of the doctor for symptomatic treatment.