Hi, my 7mth old have this redness on his left eye and its been 5days already... anyone know what is it?

It could be irritant conjunctivitis... did shampoo or soap or any other irritant accidentally splash into your baby's eyes? It could also be a burst capillary? Both are harmless and will go away in a week or so. If it stays beyond the week and baby shows discomfort or pain, maybe you should take baby to the doctor.