I'm Allergic to Daddy - S6.E21

Janet gives Kathy Jo a clean bill of health as the rash that she had has cleared. She figures Kathy Jo was allergic to something that isn't around anymore. But Kathy Jo's rash reappears when Steve returns from a week long business trip. Janet suggests Steve temporarily move out of the house to see if the rash clears while he's away. Then gossip spreads throughout the valley that Steve and Betty Jo have separated. Kathy Jo's rash clears up again. Steve is growing frustrated that he still can't go home. In the end, Janet figures out what is causing the rash and it isn't Steve.