The doctor may suspect a fungal infection if the patient exhibits a characteristic rash. If the patient also has a risk factor, there is a stronger possibility of fungal infection. If the doctor suspects a fungus infection, there are two main methods to determine the type of fungus. A technician places a sample of the rash in KOH solution and heats it. The KOH changes the rash sample so that the fungus shows up more clearly under the microscope.
Experts can often identify the fungus by the filaments it sends out through the skin sample.
Another method involves growing a colony of fungus in the laboratory from a rash sample. This is more accurate but may take weeks. Some fungi exhibit a fluorescent glow when exposed to ultraviolet light. This can also help to identify the fungus causing an infection. Find a dermatologist near you.