Coworker smokes, but I can’t live with it

My coworker smokes and they sit behind me. Whenever they come back from a smoke the smell is very intense. I need this job and cannot quit. I can look for opportunities in other departments but it’s not going to happen anytime soon. My coworker is awesome as a person and there is no hate towards them, it’s just the smell I really can’t handle because of respiratory issues. What should I do?