If you are a trip leader with a group going into the outdoors, make sure that you ask each member of your group about potential allergies while still in the planning stages. Those who have experienced an anaphylactic reaction previously are likely to experience it again, so they should always carry prescribed treatment with them, usually some form of an epinephrine injector.
Be aware of potential allergens on the trail, as you or others may not know if you will have an anaphylactic reaction in response. Look out for bees, wasps, hornets, yellowjackets, and fire ants, as the venom in their bites and stings may cause anaphylaxis in susceptible individuals.
If someone in your group has a food allergy, then everyone on the trip should be made aware. If possible, everyone should refrain from carrying the food allergen. For example, if someone is allergic to peanuts, then no one should carry trail mix that contains peanuts, as some anaphylactic reactions occur after a person ingests the allergen, but some will occur upon contact with the allergen, and being in a remote location can confound the issue.