Menu Healthy Lifestyle Diseases & Conditions First Aid Symptoms Tests & Procedures Videos Definitions FAQs OnychomycosisUpdated: 2017-06-13OverviewOnychomycosis is a nail fungus. It causes thickened, brittle, crumbly, or ragged nails.SymptomsRarely, the condition causes pain or a slightly foul odor. Usually the problem is cosmetic.TreatmentsTreatments include oral antifungal drugs, medicated nail polish or cream, or nail removal. © 1998-2022 Mayo Foundation for Medical Education and Research(MFMER). All rights reserved. Terms of Use