Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Exogenous ochronosis ?
    ### Response:
    Exogenous ochronosis refers to the bluish-black discoloration of certain tissues, such as the ear cartilage, the ocular (eye) tissue, and other body locations when it is due to exposure to various substances. It has been reported most commonly with topical application of hydroquinones to the skin.
    