It would be to warn potential guests with pet allergy issues that there has been an animal in my place recently. That's just what I would do for my own business ready listing. Others may want to handle it differently.
Example, I host a guest with a seeing eye dog for a month. For my next guest, I get an instant book from someone with severe dog dander allergies. They picked my place because it is "Business Ready" and is not supposed to have had animals.
Best case: I learn they have allergy issues before they check in and tell them about the dog, they cancel and we work with airbnb and give them a full refund and no penalty for me.
Worst case: They arrive and have a bad asthma attack. I tell them about the previous guest with a seeing eye dog. They cancel and demand a 100% refund. Airbnb will probably give them a full refund. Even if airbnb does NOT penalize me, I'm still left with a vacant space and a few lost days of income.
Both cases are a lot of trouble for host and guest. It's not your fault, you had to accept the seeing eye dog. The only way I see to avoid this is to put it in your decription if you IB or mention it to every potential guest if you don't do IB.