15 month old dihera, fever cough runny nose red eyes pale horse not wanting to eat and drink what is causing it?

Many reasons. There are many causes for this, most are viral. Since your child does not want to eat or drink (drinking is the real problem), your child needs to be evaluated. If your child does not urinate at least 3 x in 24 hours, your child could be getting dehydrated which warrants an evaluation.