Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Vernal keratoconjunctivitis ?
    ### Response:
    Vernal keratoconjunctivitis (VKC) is a chronic, severe allergy that affects the surfaces of the eyes. It most commonly occurs in boys living in warm, dry climates. Attacks associated with VKC are common in the spring (hence the name "vernal") and summer but often reoccur in the winter.
    