red rash on neck, chest and back

[HLS]

My 8 month old has had a red rash around her chin, neck, chest and all over her back. It's also on her hands and a bit on her feet. She is
dribbling a lot due to a tooth coming but I
canno see why the rash is also on her back. Sometimes its raised bumps and sometimes just a rash. Does anyone know what this is.

 

[BunnyFace]

Have you changed washing powder or anything like that? Id take her to the doctors, see what they say