What causes ingrown toe-nails to form?

Reasons for ingrowns: This annoying condition is usually the result of clipping the corners of the big toenails so deeply and sharply that a small sharp fragment of nail is left. As the nail grows, this sharp spear is jabbed into the nail-fold, breaking the skin and instantly becoming a foreign body. The body attacks, and the rest is history. Treatment consists of removing the fold of skin and the spear.

Several things: Improper cutting of the nail, trauma, tight shoes.

Tight shoes: Improper cutting, trauma or injury, genetic are some common causes.