The meds you've described are not known to commonly cause cataracts; however, the side effects can be unique to an individual in any case.
The reason I wondered about the diagnosis of cataracts in a dog this young (you did indicate under 5 years old right?) is because a couple other conditions are frequently mistaken for cataracts.
Most cataracts in dogs are inherited (do you know her history?) In a young dog, if it's cataracts and not genetic, other causations might be trauma, glaucoma, retinal degeneration, nutritional deficiency, Cushing's or diabetes and even as the result of toxins.
It's just perplexing to think that in a youngster like this, if there's no familial history of them, that it would be cataracts. I suppose she may be reacting to the steroids as a toxin, but I'm really reaching with that.
I'm happy to hear that you're seeing a specialist soon (I think the sooner the better since even if it's cataracts, it's often successfully treatable with removal, similar to what they do with humans).
Until then, since it sounds like her allergies are signficant, continuing those treatments is prudent. You're working well with her vet on this and can obviously trust him.
Do you recall the specific (if any) diagnoses with regard to her allergies?
This link might help with more info about allergies, but it does seem you've become an expert on that one Images available only to Customers.
http://www.dogo.org/Education/canineallergies.asp
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You remain responsible, forever, for what you have tamed.