My 2 year old daughter has a rash in her cheeks any ideas?

Fifth disease. A common illness caused by a virus, it most commonly starts with bright red cheeks (as if they were slapped), then a lacy rash on the arms of little children. This all goes away in about 3 days, and there is no serious effect afterwards. Of course if she was out in the sun without sunsreen on her cheeks she may get a sunburn there.