Barry Allen, in The Flash, doesn't have a healing factor in the sense that the term is typically used in comics. He is not able to heal wounds or injuries that normal humans could not.
What he has is accelerated healing -- because everything about his biology is accelerated, he heals the same way that a non-metahuman would but it happens more quickly. For example, if a person Barry's age were to fracture a bone in their arm or leg, it would typically take about 6 weeks for it to fully heal. If Barry were to fracture a bone in his arm or leg, it might heal in a matter of days or even hours.
However, if Barry's hand were cut off, the bleeding would stop and a stump would grow over the injury very quickly, but he wouldn't regrow a hand the way Wolverine would.