Hello, my son has this problem also. You didn't say what kind of reaction your boyfriend is having but for my son it's a very high irregular heart rate and I just wanted to say Please be careful with the Zyrtec - allergist gave this to my son instead and we ended up having to call 911 as his heart rate went over 200. It was very scary. I would also suggest (like another poster said) that if you are going to try try it, maybe do it in a allergists office where they are equipped to handle emergencies. Good luck.