To elaborate on leratiomyces contribution to the OPs query, true anaphylaxis is a serious and rapidly evolving allergic reaction (at a tissue level, dilation of blood vessels which become leaky) but the manifestations can vary from widespread hives to the more lethal picture which is in the mind of the OP, namely "anaphylactic shock" for which epinephrine is absolutely the treatment of choice.
The symptoms of anaphylaxis for our purposes can be thought of as existing on a spectrum and may start with tingling, flushing and itching, progressing to urticaria ("hives" ) which may be localised or widespread, and then on to the life-threatening features affecting the lungs (wheezing, tight chest, breathlessness), facial and laryngeal swelling (also adding to airway obstruction), hypotension, nausea, vomiting, diarrhoea (these largely represent gut edema), heart arrhythmias or even a heart attack (infarction).
For any of the life-threatening features epinephrine IM is firstline, largely to counteract the hypotension (but also to increase intracellular cAMP) but IV antihistamines and steroids would follow to deal with all the different components of the dysfunction at a cellular level. In the hospital setting the treatment would also include oxygen, BP monitoring, IV access and often IV fluids- luxuries not found in the jungle.
If ones reaction did not have features suggesting life was threatened then IM epinephrine would probably be overkill for simple hives (apparently its not pleasant!) and oral steroids and antihistamines would probably be sufficient.
Its important to note that the picture does not have to strictly follow the spectrum outlined and anaphylactic shock can rapidly develop within minutes without the preliminaries. I personally would like to have epinephrine, a steroid, an antihistamine and some salbutamol close by as mentioned in leratiomyces handy meds to have list.
I am paranoid of my brain. It thinks all the time, even when I'm asleep. My thoughts assail me. Murderous lechers they are. Thought is the assassin of thought. Like a man stabbing himself with one hand while the other hand tries to stop the blade. Like an explosion that destroys the detonator. I am paranoid of my brain. It makes me unsettled and ill at ease. Makes me chase my tail, freezes my eyes and shuts me down. Watches me. Eats my head. It destroys me.