How to Diagnose a Rash by Symptoms

The symptoms of a skin rash are key to proper diagnosis. The symptoms paired with additional information gathered from physical examination and laboratory studies help the clinician to relate the presenting symptoms to a well-known pattern that fits a specific diagnosis.

Instructions

• 1

  Determine the history of the rash. Ask your patient when the rash appeared, if it is constantly present and have its characteristics changed over time. Also inquire about any unique circumstances related to the appearance of the rash such as use of new cosmetics or soaps or about exposure to unusual environmental factors. A rash that is related in time to a new exposure strongly suggest an allergic reaction such as contact dermatitis.

• 2

  Get details on the characteristics of the rash. Be sure to find out about the color, shape and distribution. Ask if the rash is painful or itchy. Red and itchy rashes are often indicative of an inflammatory reaction as part of either an allergy or infection.

• 3

  Ask about associated symptoms such as fever, cough, changes in skin color, etc. These associated symptoms may give you a clue about possible causes such as infection, major organ disease or an uncomplicated allergic reaction.

• 4

  Use the information from Steps 1 to 3 to determine the most likely diagnosis for the rash. In some cases, the symptomatic information is enough to determine a cause but often times you will need additional information in the form of visual examination of the rash, blood tests and other laboratory evaluation.