Pets in the Workplace policy in Ontario and allergy accommodations. Whose need wins?

Several of our employees and some of our members of the public want to begin bringing their pets to work, mainly dogs for stress release and comfort. No one has a service animal. One employee has already brought a furry friend in unannounced for the day without any incident. Now other employees want to. We have a mid-sized head office and several small work locations in Toronto. We have one employee who is not keen on this due to a slight fear of dogs. We also have a member in our co-working space who has told us they are highly allergic and that they would need to end their membership if and when we become pet-friendly. We have offered to find a way to accommodate but the member explained that it is a server dander allergy and they simply can’t be where dogs are regularly present for health reasons. What risks do you see here under AODA and Human Rights and what suggestions do you have to balance the needs of pet lovers with the phobias and allergies of other people in the workplace?