Itraconazole is an anti-fungal, sometimes prescribed by veterinarians. This medication treats generalized systemic infections and infections of the skin. Itraconazole is primarily effective in combating yeast and fungal organisms. Those fungi strains are the common cause of toenail infection, ringworm (also known as dermatophytes) or skin infection. Itraconazole can also be used to treat cryptococcosis and blastomycosis, serious fungal infections.