Peanuts, or more specifically, peanut oil, can also be a problem because it is found, or shall we say hidden, in many prepared foods, particularly snack foods such as cookies and potato chips.
The symptoms of anaphylaxis often begin with urticaria, or severe itching and welts all over the body. Swelling around the face may follow, followed by elevated and heart and respiration rates rate as the victim struggles to breathe. Eventually, if left untreated, the swelling may occlude the trachea and the person dies. Therefore it is important to monitor the victim's airway at all times.
Individuals who know they have a severe allergy will usually carry an EpiPen, which is simply a spring-loaded syringe loaded with epinephrin, which is another word for adrenalin. Lay persons are not permitted to administer EpiPens, except in certain specified situations, such as trained school staff, but we can help the individual find her EpiPen and prepare it for injection by her. Injection is accomplished by removing the cap and jamming the business end of the EpiPen against the outside of the thigh and counting slowly to ten while the epinephrine is automatically injected into the patient. The pen will go through some clothing, but it will not go through car keys or coins, so slow down and make sure the area of injection is clear of objects, or better yet, actually pull up the shorts or pull down the pants to visualize the person's thigh.
If you are in the wilderness, an EpiPen may not be available. For this reason I carry liquid benadryl capsules. Benadryl is a strong anti-histamine, and will help contract the blood vessels to a more normal state. I will make a slight slit in three or four capsules and ask the victim to hold the liquid under her tongue as long as possible before swallowing it. There is huge vascularization under the tongue, and medications are immediately absorbed into the body there. The victim may also bite the capsule to open it.
I also carry two or three instant coffee servings. There is some evidence in the medical literature that coffee helps to contract the blood vessels, so I will make a couple of cups of strong, black coffee and ask the victim to drink them. Note that this is a violation of the usual rule of not giving victims anything to drink, and you would never do this in a 911 response area. But in the wilderness, things are different, and you will want to do anything that might help.
And of course don't forget to treat for shock, maintain the victim's airway and continually monitor the victim's condition.