For the itchy and bloodshot, try some artificial tears from the pharmacy. Alcon makes a good one with lubrication in it. That really helps. As for the GPC, have you done warm compresses yet? You are probably getting salt plugging up your glands in your eyes that produce oil. It's likely that's why you are getting such itchy red eyes after you work out; that oil is what keeps your tears on your cornea and elsewhere, without those glands working properly, your eyes get VERY irritated. I notice this as I have begun riding more outside. Those little salt granules on your face after sweating hard cause eye problems sometimes. Take a washcloth and put it in relatively warm water, don't burn yourself but make it as warm as you can. Leave it on for 5 minutes per eye and see if that doesn't help with the itchy, nasty eye feeling.