My baby is 15 weeks old. She has got rashes on her cheeks, don't know if I should be concerned or not. Is this normal among babies or is this eczema?

I am not sure how does your baby's rash look like but if your baby is constantly scratching his face and has red inflamed patchy skin, it might be eczema. My daughter had bad eczema which start out as a small patch and soon spread to the entire face. You might want stop using any soap on her face in the mean time and start using water to clean her face frequently.