Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Perniosis ?
    ### Response:
    Perniosis are itchy and/or tender red or purple bumps that occur as a reaction to cold. In severe cases, blistering, pustules, scabs and ulceration may also develop. Occasionally, the lesions may be ring-shaped. They may become thickened and persist for months.
    