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My female Jack Russell is constantly scratching and rips her hair out on her back. She will chew and pull till she makes bald spots all over her. During the winter months we let her hair grow out and then shave her come spring time and summer time. In the winter she doesn't scratch at all and the we shave her and she goes nuts. It is not that hot here yet and she has no fleas so any suggestions as to what it could be that causes her to rip her hair out.