One more thing. A friend and I once went up in a private plane, a small Cessna. My friend had a severe cold and didn't take a decongestant. He in fact had severe problems from the flight and lost a good deal of hearing from one ear (permanently unfortuantely). So I am very careful. Again, I would summarize what I find works

1. no anti histamines of any kind
2. take decongestant about 1 hour before descent.