It happens say once a week, I dont know if it is normal or I need to take her to the vet. There are some hair balls occationally other times are food undigested. I feed her Royal Cainn hair ball control. Is the food not right ? I comb her quite often as she is shedding much at the moment. Thank you very much for your concern. I found this web is quite helpfull . Appreciate for your answer. Cheers.