@Mustafa297
Yes...this can be a real issue for those who have extreme allergies to pet dander. I have a relative who experienced this very issue and had to cancel a stay (no refund offered by the Host) due to allergies. In all fairness, he realized he was at fault as he hadn't noticed they did accept pets.
As @Shelley159 points out, you can never be assured there was not a service animal at least in the listing, even if it says NO PETS. Your best bet is to find listings that don't allow pets, and then message the Host and ask if they have ever hosted with a service animal, even if they don't allow Pets and mention your allergies as a concern (if you have them).