Just thought I'd mention that many dogs that have a reaction to corn isn't the corn itself. It's the pesticide and chemicals that the corn absorbs during growth and not lost in processing that dogs have a problem w/. Just an interesting thought. If you eve get the chance (depending on their allergic reaction(s)) try getting ahold of some organic corn...maybe even pop corn and let them have a taste and see if their allergies flair up. I don't know your dogs, but I'm willing to bet they'd be fine!
Don't know if it's worth a risk though because like I said I don't know how badly they react to corn. If it's just itching and so on, give it a go!