What are the signs of a fungal infection under my fingernail, and how is it treated?

Fungal nail infections (onychomycosis) often cause noticeable changes in the appearance and integrity of the fingernail. Common signs include:

• Discoloration: yellow, white, brown, or greenish patches under the nail
• Thickening: the nail becomes abnormally thick or distorted in shape
• Brittleness: crumbling, cracking, or ragged edges
• Separation: the nail lifting away from the nail bed
• Odor: a mild, unpleasant smell in some cases

Treatment options typically begin with topical antifungal medications (such as ciclopirox or efinaconazole) applied directly to the nail. For more advanced or stubborn infections, doctors may prescribe oral antifungals like terbinafine or itraconazole, which tend to be more effective but require monitoring. In severe cases, nail removal may be considered.

Because fungal infections can look similar to other nail conditions—like psoriasis, trauma, or bacterial infections—it's important to confirm what you're actually dealing with before starting treatment. A free, instant, online symptom check can help you quickly assess your symptoms, understand possible causes, and figure out the right next steps—saving you time, guesswork, and potentially unnecessary treatments.

Reviewed for medical accuracy: 07/15/2026