Ingrown Nail - Causes

Causes

The main cause of onychocryptosis is footwear, particularly ill-fitting footwear, including shoes with inadequate toe-box room and tight stockings that apply top and or side pressures. Less frequent causes include the damp atmosphere of enclosed shoes, softening the nail-plate and swelling the epidermal keratin, which eventually increases the convex arch permanently; genetics; and trauma and disease. Improper cutting may cause the nail to cut into the side-fold skin from growth and impact, whether or not the nail is "ingrown" (true onychocryptosis). The nail bends inwards or upwards depending on the angle of its cut. If the cutting tool, such as scissors, is in an attitude where the lower blade is closer to the toe than the upper blade, that will cause the toenail to grow from its base upwards, and vice versa. The process is visible along the nail as it grows, appearing as a warp advancing to the end of the nail. The upper corners turn more easily than the center of the nail tip. As people cut their nails by holding the tool always in the same angle, they induce these conditions by accident; as the nail turns closer to the skin, it becomes harder to fit the lower blade in the right attitude under the nail. When cutting a nail, it is not just the correct angle that is important, but also how short it is cut. A shorter cut will bend the nail more, unless the cut is even on both top and bottom of the nail.

Causes may include:

1. Shoes cause bunching of the toes in the developmental stages of the foot (frequently in those under 21), which can cause the nail to curl and dig into the skin. This is particularly the case in ill-fitting shoes that are too narrow or too short, however any toed shoes may cause an ingrown nail.
2. Bad nail-care, including cutting the nail too short, rounded off at the tip or peeled off at the edges instead of being cut straight across
3. Trauma to the nail plate or toe, which can occur by stubbing the toenail, dropping things on the toe or going through the end of the shoes (as during sports or other vigorous activity), can cause the flesh to become injured and the nail to grow irregularly and press into the flesh
4. Predisposition, such as abnormally shaped nail beds, nail deformities caused by diseases, or a genetic susceptibility gives rise to a higher chance of an ingrown nail, however the ingrowth cannot occur without pressure from a shoe.
5. Ingrown toenails may be the result of a bacterial infection, treatable with antibiotics. See Treatments.

A more physiologically sound description is that an ingrown toenail is actually too much skin around the nail ("overgrown toeskin")—the nail is not the problem, however the ingrowth still requires the wearing of a shoe. Vandenbos and Bowers theorized that pressure necrosis of the soft tissues surrounding the nail due to weight-bearing is the primary cause of ingrowing toenails:

The term "ingrown toenail" is unfortunate in that it incriminates the nail as the causative factor and is responsible for the fact that most operative and conservative treatments are directed toward the nail. It is our thesis that persons who develop this condition have an unusually wide area of tissue medial and lateral to the nail and that with weight bearing this tissue tends to bulge up around the nail. When such persons trim the nail in a curved or rounded fashion instead of straight across, further bulging of soft tissue is allowed, and as the nail grows out, pressure necrosis of soft tissue occurs. If our thesis that the fault lies not with the nail but with an excess of soft tissue is correct, treatment by removal of a segment of nail is not rational. It increases the relative amount of soft tissue and predisposes to recurrence and at the same time inept attempts to remove some nail matrix lead to faulty regrowth of the nail. The logical conclusion is that soft tissue should be excised, so that with weight bearing there will be no tissue to bulge up across the nail.

One study compared patients with ingrown toenails to healthy controls and found no difference in the shape of toenails between patients and controls and suggested that treatment should not be based on the correction of a non-existent nail deformity. Ingrown toenails are caused by weight-bearing (activities such as walking, etc.) in patients that have too much soft tissue (skin) on the sides of the nail. Weight bearing causes this excessive amount of skin to bulge up along the sides of the nail. The pressure on the skin around the nail results in the tissue being damaged, resulting in swelling, redness and infection. In the past (and still today) the most common treatments are mainly directed at the nail (paradigm paralysis). Treatments often include removal of part or all of the nail. But since the nail is normal and the problem of too much skin around the nail is not treated, this often results in the problem returning or in deformity/mutilation of the nail.