Corns, also known as heloma, are a small area of thickened skin, characterised by a central core that presses into the skin, causing discomfort and pain. They are caused when an area of the foot is exposed to friction and pressure, resulting in a thickening of the skin in order to prevent the tissue of the foot from being damaged.

The most common form is a hard corn (heloma durum), which usually presents on the joints of the toes and under the metatarsal heads. It has a smooth appearance and is hard and dry to the touch. These corns sometimes contain blood vessels and nerve endings from the dermis.

Corns which develop between the toes are known as soft corns, or heloma molle, and have a rubbery texture and can become macerated due to the excess moisture being unable to evaporate.

Seed corns are small clusters of corns which form within a callus on the sole of the foot or around the heel. This type of corn does not usually produce excessive pain.

In order to relieve the discomfort caused by corns, it is necessary for a podiatrist, foot health practitioner or chiropodist to remove the surrounding callus as well as the core (also called a nucleus) and reduce the pressure on the dermis. Well-fitting footwear can help reduce the likelihood of  the condition returning.