Please forgive what may be a very naive question. I adopted a Maine Coon mix about five months ago and this morning she vomitted for the first time. My apologies for being graphic, but it seemed to be comprised of undigested food and a very small bit of hair. I brush her constantly since she's shedding quite a lot, but could this have been just a hairball? Her behavior before and afterward was completely normal. In fact, soon after she got sick, she ate a bit and kept it down. Is vomitting always a sign of illness? Is a trip to the vet necessary? Thank you very much.