My 3.5 week old baby girl has developed a red rash on the neck which has now extended to the shoulders and throat. I saw the HV and paeditrician on Friday and they said it wasn't anything serious and would probably pass soon. She doen't seem bothered by it as it doen't appear sore but it looks rather angry. Has anyone got any idea what it could be? It's been there for 4 days now and doesn't seem to go down.