My DS10 was diagnosed with a peanut allergy when he was two. We have carried epipens every since. I take two on planes with a Drs letter. I am always asked to take the actual pens out but I think only occassionally to show the letter. He has never had an incident. My dr actually said not to give more than two epipens for one incident as it could be too much adrenaline in the body. I thought the epipen is supposed to offset the adverse reaction so I'm confused as to why you would have to keep using multiple injections.
I am not a doctor, nor do I play one on TV

.. I am not an expert, we have been on our allergy journey for about 5 years, we have a WONDEFRUL pediatric allergy doctor and I belong to several support groups and have quite a few friends with allergy kids. I do a ton of research and keep up with all the allergy news.
Here is why we always have extra pens:
Pens can mal-function. It does not happen a lot, but it does happens. You need to have a back-up.
Sometimes mom (read me) can make mistakes. I accidentally injected myself with DS's pen once.....pen wasted.
Things can happen to pens. You can accidentally leave one in the car and it gets too hot, it can fall out of the bag, you loose your backpack.... Scary when you need one at ALL times.
When traveling, we check the pens daily to be sure the liquid is still clear and it has not been compromised.
Sometimes. one or even two shots are not enough. No, you do not want to give more than two shots, but if your child does not respond to one or two shots, and can not breath, and you are waiting for 911 to respond, you are going to give that second or third or even fourth pen. Yes, it could do damage to the heart, but the alternative is your child dying before you can get to the ER. An Epi-pen is suppose to stop the reaction, but sometimes the reaction is so severe that that just does not happen. Scary...Sick to you Stomach feeling, but something every allergy parent needs to be prepared for.
This can be an issue as you child reaches the 65lb weight limit for epi-pen jr. Something else to consider.
Benedryl- Many doctors are now rethinking using it as a first line of defense. It can sometimes mask symptoms and delay the use of epi-pens. After the child died this summer from taking a bite of a peanut butter rice krispy treat, many doctors are questioning whether to use or not, and many are now recommending using the epi-pen even if there is not symptoms and you know there was a ingestion of the allergic food.
IF THERE IS EVER A DOUBT.....USE THE PEN!!!
The thing about an airplane that scares me is how far away you are from an ER. Most times you can get a child to the ER within the 2 15 minute time frames of epi-pens. On a plane that just may not happen.
Ask all these things of your doctor.....knowledge is power!!!