R20-R23: Symptoms and signs involving the skin and subcutaneous tissue

R21: Rash and other nonspecific skin eruption

The appearance of a rash can vary greatly. Often the skin is reddened. Sometimes the skin becomes discolored or sores form on the skin.

There are many different reasons for a rash. You may not be able to tolerate certain foods or medicines, for example. Various illnesses can also cause a rash. These include inflammation from pathogens, for example.