There are many reasons for breast itching and redness upon scratching, such as breast skin allergy, breast dermatitis and breast skin eczema. 1. Breast skin allergy: Breast skin may come into contact with allergens, which can lead to redness when itching and scratching, such as wearing allergic underwear, and a rash may appear later. 2. Breast dermatitis: inflammation of the breast skin itself, which can be manifested by redness when scratching the breast itch, usually occurring unilaterally in the breast, redness, itching location is more fixed, may be accompanied by dandruff. 3. Breast skin eczema: breast skin eczema can also lead to breast itching redness when scratching, eczema cause is more complex, need to consider and a variety of factors related to, but also accompanied by a rash, oozing and other phenomena. There are many reasons why breast itching is red when scratched, and it is recommended to go to the hospital in time to improve the examination of the symptoms, and take standardized treatment under the guidance of a professional doctor, and not to be treated indiscriminately, so as not to lead to adverse consequences.