A particularly severe case:
http://www.bbc.com/news/magazine-38507160
Twenty-nine-year-old Johanna Watkins from Minnesota cannot kiss her husband Scott, or even spend time in the same room as him. She suffers from Mast Cell Activation Syndrome, a rare disorder of the immune system, which means she is allergic to almost everything, including her husband's scent.
http://www.bbc.com/news/magazine-38507160