Heinerman's Encyclopedia of Healing Herbs and Spices has many recommendations on which herbs work well for colds and flu. One of these is boneset (eupatorium perfoliatum). I'll quote you his section on using boneset for treating the flu.
Knocks the Flu for a Loop
Silena Heron, N.D. of Sedona, Arizona promotesa great "recovery therapy" during cold and flu season. Her standard recommended treatment calls for boneset, equal parts of yarrow, elderflower and lemon balm or peppermint to be made into a warm tea.
Heron encourages her patients to drink a cup of her special brew, get into a hot bath and then drink a second cup of the "flu brew" while still in the tub. After drying off, the patient should go straight to bed and cover up first with a sheet, then with a heavy wool blanket, followed by plenty of quilts. This will promote heavy sweating for an hour. Then the individual returns to the tub and sponges the body off with apple cider vinegar.
Edward Sieracki of Detroit, Michigan, who followed Dr. Heron's detoxifying regimen, reported that "twenty minutes after drinking this boneset blend tea, I started to sweat profusely. I drank another cup of the tea and went to bed. By the next morning I was fully recovered." Make the tea according to previously given instructions.
To cure a sore throat accompanying a cold or flu, just mix pinches of salt and cayenne pepper with the juice of half a lemon or lime and gargle. It may briefly burn your throat, but the soreness will quickly leave.
I haven't tried this therapy yet, but if I get the flu, I will. It can't hurt and it is always good to detox. Your body will appreciate it.
In other posts, I'll run Heinerman's flu/cold recommendations here as well.