The most common causes of ingrown toenails are shoes that don't fit correctly and improper toenail cutting (cutting nails too short or cutting down into the sides of the toes). Some other causes include: toenails which are naturally too wide, trauma (stubbing the toe), frequent running and poor foot mechanics. Active children are particularly susceptible to this condition.
Soaking the feet in a warm, salt water bath and applying a mild antiseptic with a bandage can treat milder cases. If the toe is infected it should be treated by a chiropodist who will remove the offending nail and treat the infection. If the ingrown toenail is a recurring problem than it may require a more permanent solution where, under a local anaesthesia, a portion of the nail is removed and a chemical solution is applied to prevent that part of the nail from growing back.