Medically reviewed by Amelia MacIntyre, DO Mycosis nail fungus, also known as onychomycosis, is a fungal infection of the nail unit. It is more common in the toenails because fungi thrive in warm, ...

When the acrylic was removed, I noticed a dark brown line under my thumbnail, running the full length of the nail bed and it isn’t growing out with the nail. It’s not sore and I’ve tried a ...