Please forgive what may be a very naive question. I adopted a Maine **** 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.