Below is an instruction from Human. Write a response.
    ### Instruction:
    Who is at risk for Hypersensitivity Pneumonitis? ?
    ### Response:
    People who repeatedly breathe in foreign substances are at risk for hypersensitivity pneumonitis (HP). These substances, which also are known as antigens, include molds, dusts, and chemicals. However, most people who breathe in these substances don't develop HP.
    