Ingrown nails, the most common nail impairment, are nails whose corners or sides dig painfully into the soft tissue of nail grooves, often leading to irritation, redness, and swelling. Usually, toenails grow straight out. Sometimes, however, one or both corners or sides curve and grow into the flesh. The big toe is usually the victim of this condition, but other toes can also become affected. Ingrown toenail may be caused by improperly trimmed nails, heredity, shoe pressure, or repeated trauma to the feet from normal activities.