There are many clinical diseases that cause erythematous papules, mainly seen in skin diseases caused by different etiologies, and a few patients with autoimmune deficiencies can also cause such phenomena, here are a few common cases: 1, infectious skin diseases: usually viral infectious skin diseases appear erythematous papules are more common in young children, such as hand, foot and mouth disease, early childhood acute rash, infectious mononucleosis, measles The patient usually has a history of fever before the onset of the disease, the appearance of erythematous papules accompanied by a generalized rash, while the rash site has a certain time sequence, but the rash itch is not obvious; 2, allergic skin diseases: patients with these diseases appear erythematous papules at the same time can be accompanied by significant itching, common in eczema, contact dermatitis, etc.. In addition to erythematous papules, eczema can also be seen as blistering vesicles, oozing, crusting, while the chronic phase is still visible moss-like changes. However, patients with contact dermatitis usually have a clear history of allergy and can see erythematous papules blisters confined to the contact area, and clear borders; 3, physical skin diseases: these diseases are mostly related to sun exposure or other external friction, damaging stimuli, such as common sun dermatitis, prickly heat, polymorphic sun rash, frictional lichen planus-like rash can cause patients to produce erythematous papules; 4, autoimmune diseases: these diseases are mostly due to In addition to erythematous papules, patients usually have systemic disease reactions, such as lupus erythematosus, herpes pilaris, vasculitis or vascular disease.