Hubby says he can't quit smoking because....?

he says he is allergic to smoke and that as long as he smokes, he will NOT have an allergic reaction. When he smokes, his sense of smell and taste are dulled. He tried to quit 3 other times, and failed (max. 8 weeks). Married 15 years this summer. I gave up asking. He doesn't smoke around us (we have a 6 yr old and a 6 mth old).