It could be. From rubbing or from urine. With my second son I had to get certain diapers and wipes because he was so sensitive.

Is the irritation from the diapers ? I think Vaseline does help, but it still hasn't gone away.

He's two weeks old, and his circumcision just got check at the doctors. Then a few hours after we were home we noticed it was swollen.

How old is he? They tend to get some irritation. My sons penis wasn't circumcised correctly so his got red and swollen a lot due to skin on skin contact. It would fold in on its self. I would use Vaseline and would help for a little bit. But if it doesn't clear up in about a day and a half, I would go back to the doctor and make sure it's okay.