NONE OF THIS IS MEDICAL ADVICE. Get many epi-pens. Never need them. etc.
Handling a severe allergic reaction.
One fireant sufferer mentions:
Nettle tincture with yarrow tincture (awful taste), followed by a strong brew of nettle,yarrow and elderberry tea. Works well enough I do NOT need the epipen. I also, as preventative drink nettle and elderberry tea several times a week.
Nettle and Apple Cider Vinegar have a good history of use for treating rashes. Use the nettles as a tea, both orally and applied to the site. The apple cider vinegar (ideally, "Braggs", which has the "mother" which can be used to start a batch of your own), should be diluted a little and applied directly to the skin. Doesn't hurt to add a teaspoon or so to water and sip it. They don't work as fast as benedryl, but they won't make you feel sleepy and dopey, either.
Bronchial (I can't breathe)
If you have a bronchial reaction -- shortness of breath, cough, etc. -- or facial or other swelling, a somewhat stronger remedy may be in order. Consider "Mormon Tea", aka ephedra aka ma-huang. This has the effect of opening the bronchi and allowing easier breathing. (It'll speed up your heart, too, and can make you feel jittery.) You can grow Mormon Tea at home for situations like this, but it prefers warm, sandy, dry conditions.
Unvalidated -- and note that Aconite is highly toxic:
I suggest you research the homeopathic remedy Aconite (Aconitum Napellus). It is very effective in treating the sudden onset of inflammation/swelling. Start here.