A typical response when someone sneezes would be to say "bless you"

In the United States, "Bless you," or a run-together form of "God bless you" that sounds like "G'bleshyu," or, quite often, "Gezundheit" (German for "good health.") The custom supposedly dates from the Middle Ages, when an unexpected sneeze was sometimes the first symptom of bubonic plague.

Generally We Say "Bless You" It's Very Common So Dont Worry About Thinking That Others Don't Use It Either