I know they useed to say urine from animals had allergens in it, but I wasn’t sure if moderns science still believes that, so I googled and found this : “Several allergens have been identified in Rabbit saliva, fur, urine, dander and dust, but most have not been fully characterised yet.” The article also says “While Rabbits are common as pets, severe allergic reactions to domestic Rabbits in homes are unusual. Typically, allergic manifestations are mild to moderate allergic rhinitis, conjunctivitis, pruritus and/or asthma, contact urticaria and contact dermatitis in laboratory animal caretakers with frequent exposure (4, 11-12)”. This info I got from a rather detailed text on a website that markets scientific allergy tests rabbit allergens
It’s in short quite possible for your bf to be allergic to rabbit urine. The best you can do is probably minimize his handling of the rabbit, frequent cleaning of the litter-boxes and keep modern OTC antihistamines (antihistamines that have no sedative effect) at home in case your bf gets an attack. Keep in mind they take 1-2 hours before they take full effect. Don’t use antihistamines of the old type, those that have a sedative effect (benadryl f ex), that can be dangerous in combo with driving etc.
I’m sorry about your bf’s allergy. It’s good that you changed the hay to orchard since allergic people often are allergic to more than one thing, and they all add up. Timothy is a grass that many allergic people can’t deal with. The spring is generally the worst period for allergics because their system has to deal with all the tree pollen and grass and everything as well.
Allergies to furry animals is often worst with young animals. I am allergic to cats but kittens are WAY worse than adult cats for me. I also react to timothy hay so I’ve switched to oat and orchard.