Why isn't dermatology called External medicine?

Answer 1

Because dermatology is the study of disease of the skin.

The Dermis is the skin. Therefore, dermatology, you dont call the study of the heart heartology or heart medicine do you? No you call it cardiology because its the cardiovascular system.

and if you are thinking it as in reverse of internal medicine, internal medicine is the study of disease of the whole body both inside and out.

Answer 2

Skin is the largest organ of the body. It is a living organ . Active metabolic processes keep on occuring in skin throughout our life. Skin maintains human temperature constant. Skin eliminates waste materials and helps in protecting the body from infection. Skin is a part of your body.