@Lorna170 I hear ya. Probably for the same reason that people ask for discounts instead of finding a place that suits their budgets, or choose places with a strict cancellation policy but go mental when the host upholds it. If I were being generous, I'd assume that people like this simply lacked the foresight to account for contingencies when making their plans.
However, your guest's wording strongly suggests that she's setting you up for entrapment and fully intending to use Airbnb's gaping loopholes around Covid to squeeze you for a refund the minute she spots a stray hair. The recent cleaning mandate appears to grant guests a full refund if they accuse a host of not following the protocols, and your guest has already drawn a straight line between adherence to the Cleaning Standards and the presence of allergens (real or imagined).
I would never advise hosting guests who demand an allergen-free experience, especially when their problem could be easily solved by choosing a more appropriate listing. Guests who ask are entitled to know what cleaning processes you use in preparation for their stay, but I recommend adding the caveat that you can't guarantee an experience free from pet-related allergens - and suggesting that those with a high degree of sensitivity cancel and book elsewhere.
One thing to note: the fact that you're pet-friendly makes your listing an especially poor fit for this guest, but Airbnb's disability policy largely prohibits Entire Home hosts from refusing assistance animals or emotional-support animals, who shed just as much dander as a plain old pet. As long as this controversial policy is in place, people with animal allergies should not assume that a "no pets" home hasn't been occupied by someone's Emotional Support Buffalo or whatever.
