Discussions that mention zyrtec

Allergies board

Antihistamines definitely work better if they're taken before exposure to the allergen so your best bet is to try giving her the Benadryl at least an hour before going to the house with the cat (you might even try Zyrtec instead of Benadryl because it won't make her drowsy and is longer lasting).

Unfortunately, antihistamines aren't foolproof and cat dander can be tough to avoid so you probably just have to give her the antihistamine and keep an eye on her.