Am I having an allergic reaction to my new acne medicine?

[Mountain Ash]

I just started using Clinique skin care because I heard many things about how gentle it is. I've never had any problems with acne medicine before, but the old one I had wasn't working very well anymore so I decided to switch.

The clinique seems to be working very well - the acne on my neck has gone down noticably in the week since I started it, but directly after applying it my neck gets very red and itchy. It goes away after a few hours, but it's so distracting I've stopped the night treatment because it was keeping me from getting to sleep.

Is this an allergic reaction? Or is it a natural reaction to the medicine? I've never had an allergy before, and the red itchiness goes away on its own. Plus, the treatment is working really well and I don't want to the acne to come back. Suggestions would be greatly appreciated.