My cat did that for a while so I know how much of a concern it is.

I never found a solution (though didn't try acupuncture). The vet thought maybe allergies but it was never isolated. My cat eventually grew out of the habit- though for a while her entire stomach area was bald.

In retrospect, I think it was more due to loneliness and anxiety resulting in 'hyper-grooming.' I had started a new on-site job and was away more than usual during the day.

Anyway, hope it resolves!