### Human:\nwhat exams and tests help doctors to evaluate or test people for ringworm of the skin?\n\n### Assistant: doctors often can easily recognize ringworm by its ring-shaped rash. your doctor will probably also look at a skin sample ( koh preparation ) under a microscope to confirm that fungus is present. tests for ringworm of the skin include: a koh (potassium hydroxide) preparation. this test can help your doctor find out whether a fungus is causing your rash. the doctor will take a sample of your skin by lightly scraping the infected area. the sample is placed on a slide with potassium hydroxide (koh) solution and gently heated. if fungus cells are present the doctor can then see them with a microscope. a fungal culture ( skin culture ). this test can identify the type of fungus that is causing your infection. usually a culture is only done if the diagnosis is difficult or the skin condition is not responding to treatment. this test may take up to 4 weeks because it takes time for the fungus to grow. webmd medical reference from healthwise this information is not intended to replace the advice of a doctor. healthwise disclaims any liability for the decisions you make based on this information. © 1995-2011 healthwise incorporated. healthwise healthwise for every health decision and the healthwise logo are trademarks of healthwise incorporated.