Treat. Definitely. Doxy will not hurt the dog. I just put one of mine back on Doxy because his effort level seemed down. He was intially treated with 6 weeks of doxy at 400 for 2 weeks, then 800, then 400. If he shows an improvement in his effort level, may keep him on long term..... There are some very well know field trialers that are now keeping their dogs on Doxy year round, and some do a course annually.