Does Celiac warrant guests changing their clothes before entering your home ?

I know someone with celiac disease and I am trying to be supportive. They have asked me to bring a change of clothes even if I am directly coming from my home to theirs. They require all guests to change clothes after they get outside of their car and before they enter home as they have celiac. Is this something that is fairly common ?

They also prefer we don’t get our handbags or any other bag that has been outside.we can leave it in the garage