Skin is the largest organ in human body. Human skin is an integument of the surface of body acting as a defensive cover and receiver of sensory stimuli. It is necessary to sustain human life as it protects the organs, tissues and other parts of body against external environment like dust particles, microbes etc. It also regulates body temperature and provides sensation of heat, cold, touch and other sensation. There are three layers in skin of human body. The outermost layer of skin is called epidermis which provides waterproof barriers. The epidermis has special cells called melanocytes which affect the skin color. The layer beneath the epidermis is called dermis and it is composed of tissues, glands and hair follicles. The lowermost layer is hypodermis which is made up of fat and connective tissues. The skin and its related tissues are sometimes effected by diseases which are called skin diseases or cutaneous condition. Some of the diseases can be harmless, whereas some diseases can cause serious discomfort and pain. Some of these diseases are even fatal.

Generally, diagnosis of skin diseases is done by dermatologists with acquiring necessary information regarding skin abnormalities, symptoms, duration, color, texture etc. Dermatologists uses imaging techniques which helps for better observation of skin surface and its various forms. These techniques rely on the expertise of the specialists which led to the need of Computer Aided Diagnostics (CAD). It can be used to accurately and precisely diagnosis diseases related to the skin. This technique also helps in providing diagnosis and prediction of diseases to people residing in far flung areas where the availability of specialists may be very less. The steps involved in creating a CAD system are pre-processing, lesion detection and identification and lesion classification. Among these, lesion detection and identification is an important part as it results in the better accuracy of classification of skin lesions. But one of the main challenges in lesion classification is the availability of a wide variety of lesions in the human body. The types of lesions can be varied on basis of size, texture, color, frequency, etc. To detect the skin lesion is also crucial technique.

An abnormal growth or sore in the skin surface is called skin lesion. Some of these lesions can be harmless, whereas, some of them can be harmful and malignant. Some of these lesions are precursor to fatal disease and if not treated properly and timely can cause death also. Skin Lesions are the area in the skin surface which differs in appearance than the surrounding area. These differences can be of color, shape, pattern and dimensions. Lesions on skin can be detached or can be in group. It can be spread in single area or throughout the body. Lesions in skin are quite common and can be caused by various factors like sun burn, accidents, insect bites, etc. Some of the lesions can be caused by diseases like diabetes, skin cancer and many more. A skin lesion is also known an eruption. They are categorized as primary lesions, which are found in normal skin, and secondary lesions, which occurs due to secondary eruptions.