Diagnosis

Most of the time,your health care provider can diagnose ringworm by looking at your skin.The fungus may glow when your skin is examined with  a blue light known as Woods Lamp Test in a dark room.

Tests to confirm the diagnosis may include:

KOH Exam

Skin Biopsy

Woods Lamp Test

Skin Culture

 Woods Test: 

This test is done under black light (UV Light) with a magnifying lens.Only 50% of microsporum canis is visible under this as  fluorescence colored spots.This coloured material is not the actual fungi but is the excretory product of the fungus which sticks to the hair.

Microscopic test:

 The doctor takes some hair samples from the infected area and mixes it in a staining solution to view under the microscope. Fungal spores may be viewed directly on hair shafts. With this method doctor can identify a fungal infection for about 40%–70%  but cannot identify the particular species of fungi.

Culture Test: 

This is the most effective method but its also the most time-consuming way to determine and confirm the ringworm infection .In this test, the doctor collects hairs from the infected area, or else collects fungal spores from the hair with a toothbrush, or other instrument, and inoculates fungal media for culture. The culture is viewed using a microscope, or is sent to a pathological lab. 

Often dcotors could easily identify the rash at the first look after looking at the ring shape of the rash.

Once diagnosed,treatment is prescribed by the physician,based on the severity of the infection.