These fungi can cause patches of hairloss (usually bald circular areas) sometimes with flaking or crusting and occasionally secondary bacterial infection. The infected hairs break off close to the skin. Fungal spores on these hairs can survive for over 12 months both in the environment and on carrier animals which may have no clinical signs. Young animals are more susceptible than adults.

Diagnosis may be made using ultaviolet light "Wood's lamp" in the case of Microsporum canis which glows with a blue-green flourescence. Other Microsporum and Trichophyton do not show up with the Wood's lamp. Hair samples can be stained and examined microscopically for fungi or fugal cultures can be undertaken.

Topical antifungal treatments including ointments and rinses help to reduce skin contamination and will resolve smaller areas. Giseofulvin is given orally at 50mg/kg daily for up to 6 weeks to treat more generalized cases. Removal of contaminated hairs from the environment with procedures such as vacuuming and antifungal sprays are an important part of controlling an outbreak.