Having been treated for *presumably* food-related anaphylactic episodes over the past 30 years, several of them so severe as to require multi-night hospital stays, let me add several points to all the good information here.
1: You will never have an anaphylactic response to an allergen until you have eaten or ingested it twice. The first exposure is required for your system to produce antibodies, the chemical "trigger" which, when activated by subsequent exposure, produces the allergic reaction. Hence it is entirely possible, particularly in situations like a shipboard buffet where many of the items offered may not be those one eats regularly, to unknowingly eat something that can potentially kill you.
2: While it is always advisable to carry an Epi-Pen (or two, as noted here: more can't hurt you; less can) if you have experienced episodes in the past, your physician may (and depending on your situation, probably should) advise you to carry IM (injectable) Benadryl - a fast acting antihistamine - and oral Prednisone, a steroid. The antihistamine quickly short-circuits the release of histamines which cause urticaria (hives) and lower blood pressure. Prednisone, usually prescribed for a brief (3-5-7 days) tapering dose, where one first takes a fairly substantial amount and lowers the dose each day, is a longer acting anti-inflammatory which protects against a recurrence of the allergic response. This is particularly important in situations like travelling, where immediate critical care is not always available.
3: While there are those of you here who know which foods cause you problems, some allergies can never be identified. I have been hospitalized (ER or inpatient) more than 40 times for allergic reactions. I had a heart attack at the age of 30 as a consequence of one, and I have been intubated for respiratory support several times. I have been unconscious as a consequence of these episodes despite having self-administered the meds listed above, and have, on at least two occasions, had no (or very low) measurable blood pressure for a brief period. I have been tested - repeatedly - for allergies and no meaningful antagonists (items thought to potentiate the response) have ever been ID'd. The condition, while not rare, is not that uncommon: it's estimated that 100,000 people in the U.S. suffer from what is called idiopathic anaphylaxis: allergic reactions of unknown etiology, i.e. they don't know what triggers the episode.
I have been told by several of the allergists I have seen (including one at the NIH in Bethesda, Maryland) that allergy testing, per se, is limited in its overall effectiveness so as to render many of the test results less than reliably diagnostic. The test results are guides in many cases, but not absolute predictors.
4: Some allergists believe that episodes can occur, or occur with greater severity, when exercise is combined with the ingestion of the trigger. By exercise, btw, they don't mean running a 10K; something as benign as walking, dancing, or moderate physical exercise can set off a response which might not otherwise have occurred had one simply remained at rest. Given the myriad activities offered on a ship and in close proximity to mealtime (which can be 24/7 if you want it to be: breakfast then a swim; lunch then a jog; dinner then the disco) it's surprising to me there are not more unfortunate episodes like the one discussed here.
I have twice been well-treated for these episodes on cruise ships, once on the CRYSTAL HARMONY for a very severe anaphylactic episode which was quickly and skillfully (hey, it happened after lunch and I was dancing with her that evening) treated by a nurse while the doc was ashore and once on the Celebrity INFINITY. I have required hospital treatment in places as different as Berlin, Honolulu, and Toronto, and I have, so far successfully, been able to treat myself on other occasions at home, on ships, in hotels and twice on aircraft in flight.
I'm not offering my own experience as one I'd wish on anyone, and I'm all the more grateful for the second and third and fortieth and fiftieth chances I've been given, but it's led me to several conclusions, the first of which I learned in the Boy Scouts: be prepared. When you don't the cause, you can hardly avoid exposure to it, but you can try to limit the downside by knowing the early warning signals (flushing, itching, etc.), knowing in advance where medical care can be found and having a plan to get there, and by making sure you have the meds with you all the time and either know how to use them yourself or that someone with you does. It goes without saying that if you do know the trigger(s) you should avoid them, but again, that's not always possible. Finally, this condition has an upside. I've been lucky (knock wood) to have received so much skilled medical care every time I needed it and have - as a consequence - met and come to know some terrific people: doctors and nurses who work hard to find answers which aren't always obvious. In addition, I owe my life, literally, to some hotel desk clerks, and flight attendants, and cops and EMT's too.
Most of all, though, this condition has motivated me to see and do more than perhaps I otherwise would. When any day could be my last - which, when you think about it, is true for all of us - I think I value all of them more.
It's always a tragedy to see someone die, more so when that person is (and so often they are) young. In all honesty, my opinion is that all the preparations one might take don't guarantee a good outcome. Sadly, some of the 125 deaths mentioned probably could not be avoided. Without knowing any of the facts in this case, it's pointless to speculate why this young man died but it's not pointless to urge anyone who's ever experienced even a mild allergic episode to get good medical advice before you travel, to avoid those items you have had problems with before, and to have a plan when and if something does happen.