Pretty much all of the pertinents have been mentioned, but as someone who both carries an Epi pen (for a shellfish allergy, so I tend to be pretty lazy about it) and who is a paramedic, I'd like to reiterate the importance of carrying benadryl and taking the two in conjunction with one another. In the states that I've been certified in (PA, NY, and Nationally), the standard of care is to deliver both drugs to the patient. Epinephrine is very fast acting, but also has a short half-life in the body so the effects wear off rather quickly (think 10-15 minutes); benadryl works a bit slower, but lasts far longer. My rule of thumb is that if I think I've had a reaction, I'll take a benadryl (or two) and wait to see if the reaction progresses, but if I know that I'm having an anaphylactic reaction (a situation I've thankfully never been in) I'll hit myself with both.