Has it ever been explained what this talent actually is? If you don't have it are you unable to heal yourself? I'm curiours about Medicine as well. Perhaps it decreases the amount of Omni-Gel you need to use?

I am also wondering about that. I don't think we can heal in the game without obtaining one of those.

Leveling up your first aid increases the precentage of health gained by in game first aid "y" and lowers cooldown rate.

From what I read it also pools the First Aid abilities of all squad members as well. So if you dont have it, give it to one of your squadmates.