I feel really uneasy saying this because I don't want to discourage you from seeking veterinary help. But here goes.

Chlorpheniramine maleate (a human allergy medicine available in generic form) is safe for cats. My cat takes 1 mg (1/4 pill) twice a day (ground up in a mortar/pestle, dissolved in water, and mashed up in his smelly canned food) for a skin allergy. I suppose it might help a respiratory problem too - it does in humans - but this is really a shot in the dark, as I'm not a vet or an MD. You'd be gambling. If you choose to use this, be warned that it can make a cat sleepy and their poops mushy. Make sure it's the ONLY ingredient in the medicine, as many human medicines either haven't been tested in cats or have been tested and found dangerous.

Love, Columbine