rash?

I'm a FTM, and my 3-month old has a rash on his face, arms, and legs that I can't figure out. I don't think its eczema since it's not blistering, not dry skin since there is no flaking, and I doubt its baby acne, since it's on his arms and legs too. I spoke with a nurse at my doctor's office and she said it didn't sound like those 3 things either. If it doesn't clear up by tomorrow I'm going to call for an appointment. Any moms out there have any ideas what it can be? BTW, he has some drool rash around his mouth that looks quite similar and is clearing up with a little lanolin.