What do atheist say when someone sneezes?

Answer 1

If you mean "Do you say 'God Bless!' when a atheist sneezes?" the answer is "Who cares." It would be more appropriate to offer a Kleenex or ask if he has a cold or allergy. But saying something that gives the impression that you think diseases are caused by angry deities or that he might have coughed out his soul are traditional.

I Say God Bless you if god were to exist

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Nowadays it's usually just "Bless you!" irrespective of any religious belief.

Answer 2

It truly depends on the person. For example when someone sneezes around me (being an atheist) that I don't know or know to be religious, I will gladly say bless you. Why because it is 2 meaningless words that will make the person feel comfortable. But each person is different, and most won't say anything at all.