DNBrown makes an excellent point when saying:
"One factor besides swelling and breathing difficulties I feel I should
mention is blood pressure collapse."
The main purpose of the Epi-pen is to help keep the blood pressure up so that a
person having a reaction does not go into "anaphylactic shock".   If this
happens, the brain and all other organs are not receiving oxygen and everyone
knows what that leads to.

I've heard mixed reports of Epi-pens, mainly that one should keep them in a
cooler or thermos and not carry them around in the heat.  Our hives are near the
house, so we put one in a pocket when we go out.  If the pen contains discolored
fluid or if there are particles or precipitates in it, it should not be used.
Check the date on the pen and get a new one when it is out of date.

Several years ago, one of my sons was on a build-up program of allergy shots for
allergies other than venom( such as molds, grasses, house dust and mites) when he
had a reaction on the way home.  It started with itching, whelps, and wheezing.
His father did not recognize what was happening, but fortunately, my astute
mother-in-law did and immediately returned my son to the doctor.   After about 2
hours of meds, the first of which was epi,
he got much better.  He has had no further reactions and uses allergy shots
regularly.
Our physcian gave us scripts for Epi-pens for everyone in the family who was with
our son to keep in their home or vehicle "just in case".. My brother had one in
his vans, improperly stored and out of date for about a year.   On his job, he
was stung by a hornet, never before had he a problems with insect stings, but
while returning to his van, he realized he was in trouble.   He barely managed to
open the door, found the pen on the console and stabbed it in his thigh through
his pants.  He recovered enough to go where he could get help and was taken by
ambulance to the ER.  The doctor told him how lucky he was, without the Epi-pen,
he would have died.
The moral of the story is:
1. You do not have to be known as allergic to have a reaction.  People rarely
react with the first sting of their life.
2. You may not have much time to react before becomming unable to help yourself,
keep the Epi-pen close at hand.
3. Please store the epi-pen appropriately, and you will not have to use a bad
one.
4. Seek medical advice before you have a reation to a sting!