Symptoms of fungal nail infections vary. Your symptoms will depend on the type of infection you have. An infection can cause discomfort but is usually not painful. Athlete's foot is often present.

Distal subungual onychomycosis, the most common fungal nail infection, is caused by dermatophytes. It affects both the nail and the skin underneath the nail (nail bed). Dermatophytes cause 90% of all fungal toenail infections.¹ Symptoms include:

• Yellow streaks in the nail bed and on the underside of the nail.
• Buildup of bits and pieces of skin and nail fragments (debris) under the nail.
• A discolored and thickened nail that may separate from the skin under the nail.
• A brittle, broken, and thickened nail.

White superficial onychomycosis is a fungal infection of the nail surface. It is the second most common fungal nail infection and is also caused by dermatophytes. Symptoms include:

• White spots or streaks on the nail surface.
• Soft and powdery nail surface, as the infection gets worse.
• Damaged, crumbly, and brown or gray nail surface. But the nail does not separate from the skin underneath.

Two other types of fungal nail infections are uncommon. Candida onychomycosis is a yeast infection of the nails. Proximal subungual onychomycosis accounts for about 3% of all fungal nail infections.² But it is more common in people infected with the human immunodeficiency virus (HIV).

Conditions with similar symptoms

Only about 50% of all nail infections are fungal infections.³ Conditions with similar symptoms include:

• Eczema, a long-lasting skin disorder that may result in thickened and scaly skin. When it occurs on the hands, it may look like a fungal infection of a fingernail.
• Psoriasis, a long-lasting skin condition that causes raised red or white patches topped with silvery, scaling skin. The patches can appear on the nails. But the pitting of the nails that occurs in psoriasis does not happen in fungal nail infections.
• Reiter's syndrome, a bacterial infection that may result in changes of the nails.
• Pachyonychia (elephant nail), a very thick fingernail or toenail.
• Darier disease, an inherited skin disease in which the skin slowly hardens.
• Lichen planus, an uncommon, recurring skin disease that results in itchy, shiny, reddish purple spots on the skin.
• Norwegian scabies, a rare and severe form of scabies.

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