What can you use to remove hair gel?
Yikes.

As far as I'm aware, a thorough application of ordinary soap or washing-up liquid should be able to wash this off using the normal surfactant processes (binding to organic components with lipophilic regions of the molecule). If you're experiencing long-lived after-effects (say, more than a week maybe), you might want to see a doctor -- it's not impossible you could have had some sort of allergic reaction. Oh, and if you're going to wash hair with soap or washing-up liquid, I'd suggest using conditioner afterwards, to reduce the long-term damage incurred by stripping the natural fatty acids and oils off.

I'm not a medical professional or a tricologist, though, so please don't take this as Official Medical Advice.