What Causes Ingrown Toenails

Ingrown Toenail Causes Related to Foot Care

Shoes and socks that are too tight

The #1 most common cause of ingrown toenails. Shoes that are too narrow, too low or too short compress the toes and force the nails against the toe. Socks are frequently so tight that they draw the toes together causing increased pressure from the nail.

Improper toenail trimming

The #2 most common cause of ingrown toenails. Many individuals make the mistake of cutting the corners of their toenail too short, thus more sharply focusing pressure from the side of the nail. Shortening the nail allows the skin to fold over the toenail’s sides and free edge creating a point of pressure. Another mistake is leaving edges that are too sharp, thus enabling the nail to more easily puncture the skin.

Trimming the toenail sides at a steep angle, in an effort to relieve ingrown toenail pain, can permanently change the shape of the nail making the sides curve into the skin.

Nail shape

The shape of your toenail can change due to care, health and age. A nail that has become more arched or curved will increase the force from the side of the nail against the toe.

Un-ventilated shoes and hygiene

Toenails absorb moisture causing them to soften and change shape within the continuous moist environment of un-ventilated shoes. Over time this will cause the nail to increase its curvature permanently. Aside from this, poor hygiene predisposes a person to fungal infections and nail thickening which can also lead to ingrown toenails.


Injuries can alter the shape of the nail making it more prone to becoming ingrown. Permanent changes in shape take effect that force the edges of the toenail to dig into the skin. Examples of trauma to the toe are having something heavy fall on the toe, stubbing the toe, accidentally kicking a heavy object, and repeated pressure from activities like running.


Normally the weight of our body is spread evenly across our entire foot. But the toes carry more of our weight when running, jumping and changing direction. Higher pressure placed on the toes can cause ingrown toenails. This is amplified when the shoes required by athletes are tight fitting.

Children tearing their toenails

Children's toenails are very thin. They will frequently tear or peel their toenails off instead of trimming them with a nail clipper. Essentially the same as trimming the nail too short, this results in sharp edges that injure the surrounding skin thus causing ingrown toenails. Parents should prevent their children from doing this. Teach them the dangers in having their nail the wrong shape or too short.

Ingrown Toenail Causes Related to a Medical Condition

Excessive sweating (Primary Hyperhidrosis)

Primary Hyperhidrosis is excessive perspiration or sweating of the hands and feet. Also known as Diaphoresis. This contributes to the dampness within your shoe that cause increasingly curved toenails.

Toenail fungus (Onychomycosis)

Fungal infections of the nail result in thickening and deformities, making the nail more prone to growing inward, becoming brittle, or exerting pressure on the lateral skin folds.

Bone spur (Subungual Exostosis)

Subungual Exostosis is a bone-like tumor that develops under the toenail or occasionally the fingernail. It's most commonly caused by an injury to the nail. Because it occurs under the nail, it forces the center of the nail to raise. The growth itself is not usually painful but the changes that occur to the nail are. The nail will change shape becoming more highly curved. This results in what is known as a pincer nail. The bone spur can often be seen protruding from under the free edge of the nail.


Diabetics are particularly at risk for many foot problems including ingrown toenails due to lower blood flow to the feet.

Other Ingrown Toenail Causes


Certain individuals are predisposed to having ingrown toenails due to hereditary traits that dictate the shape and form of the toenails. Those with curved and thick toenails are more prone to getting ingrown nails, since the nail edges tend to curve into the flesh when they grow. This is also the case for those with wide toenails.


As people age, the growth of their toenail naturally slows. The nails tend to become more curved, thick and difficult to cut, predisposing the nails to brittleness and damage.

Toenail thickening

Toenails that are thicker tend to be more brittle, and thus the edges can split more easily, increasing the tendency for an ingrown toenail. Thicker toenails also tend to apply greater pressure on the skin beside the nail.

Poor dietary health

Though diet is not largely associated with the development of ingrown toenails, severe nutritional deficiencies can cause nail defects like increasingly curved toenails, thick toenails, toenail separation and weak nail structure.

Poor posture

Unhealthy posture that causes you to place more pressure on your toes, especially when standing. This constant pressure can then increase your chances for ingrown toenails.