The allergens most liable to trigger anaphylaxis are drugs such as penicillin and some other antibiotics, insect venoms and foods. While anaphylaxis can swiftly kill, not all anaphylactic reactions are fatal. Nonetheless, anyone who has ever experienced a severe, body-wide allergic reaction must be on guard and take precautions.
The origins of anaphylaxis were first explored in the 1920s, when horse serum — used to make vaccine for diphtheria, scarlet fever, tetanus and tuberculosis — was found to induce fatal allergic shock. Since then, it’s become clear that severe allergic reactions do not usually occur the first time someone encounters a foreign allergen, but only after the person has been sensitized (perhaps unknowingly) to a particular substance.
In a few instances — especially in children — an anaphylactic attack seemingly occurs on the first exposure to a food or drug, but in such cases it’s assumed the child was unwittingly sensitized — perhaps during breastfeeding, by substances the mother ate, or perhaps by hidden ingredients in a food or product.
What Exactly Happens in Anaphylaxis?
In essence, anaphylaxis is a systemic allergic reaction affecting many parts and systems of the body at once; it is the culmination of many immune-system events. As potent allergic mediators are discharged, they have a dramatic impact all over the body. Widespread, itchy hives may erupt on the skin, and perhaps also a spreading flush (redness and sense of warmth).
Along the respiratory passages and in the lungs, the mediators produce swelling and congestion which can constrict the airways and hinder breathing. In the mouth and digestive tract, the mediators can make the tongue, lips and throat tingle and swell up. Sudden smooth-muscle contractions may produce nausea, vomiting and diarrhea. In the circulatory system, the mediators may trigger blood-vessel leakiness and expansion causing a dramatic drop in blood pressure, and perhaps also heartbeat irregularities. So many serious, even life-threatening events occurring all at once can kill within minutes, through heart failure or breathing problems.
While anaphylactic reactions are frightening and some are potentially fatal, most cases do not end in death.
On the whole, the severity of anaphylaxis does not worsen from episode to episode, but this is not a foolproof rule. With time, if there is an extended period between anaphylactic attacks and re-exposure to the same allergen, the risk and severity of the reaction may fade, but this cannot be relied upon.
For safety’s sake, one must assume the worst — that the reaction could be severe —and act accordingly.
How common is anaphylaxis?
We don’t know exactly how often anaphylaxis occurs, or how many people die of it, but the condition is thought to be under-reported. The annual recorded incidence in the U.S. is about 3.2 cases per 100,000 people, or 8,000 cases a year, with 0.4 to 0.5 fatalities per million people per year — about 500 deaths a year, mainly from allergies to drugs, insect stings and certain foods. Statistics from the Canadian Allergy/Asthma Information Association show a proportional number of deaths in Canada from similar causes.
Deaths from anaphylaxis may occur away from home or far from medical aid, perhaps because someone fails to recognize the crisis and doesn’t use (or delays using) life-saving measures, or has forgotten or neglected to carry an emergency injection kit. Experts believe that allergies may be responsible for more deaths than statistics reveal; the signs of a fatal allergic reaction (the skin weals, swollen throat and flushing) fade fast, so the sudden death may be wrongly attributed to a heart attack or other event.
Recognizing Anaphylaxis in Time Is Vital
Regardless of the trigger, the signs and symptoms of anaphylaxis are usually similar. The tissues and systems most affected are those rich in mast cells — the skin, lungs, tongue, throat, respiratory tract, blood vessels and digestive system. Symptoms usually surface within minutes — sometimes within seconds —of swallowing, being injected with or (occasionally) inhaling the allergen. The key warning signs are a rash or hives, itching, flushing, tingling ( “pins and needles”}, tongue swelling or burning, throat swelling, anxiety, faintness and a racing pulse.
More than 80 percent of those afflicted develop widespread hives and swelling during an attack; 70 percent have upper and lower respiratory tract symptoms and wheezing or breathing trouble; 25 percent have a drop in blood pressure with accompanying dizziness or lightheadedness. But not all allergic symptoms necessarily occur in all people on all occasions. Some people can hardly breathe but have no obvious heart irregularities; or heart failure can occur without obvious breathing problems.
Quite often, people who experience an anaphylactic episode have no idea what it was or why it happened, and don’t bother to follow up. They may brush it off as a fluke, leaving themselves open to an equally or more dangerous reaction next time around.
Recognizing the reaction and knowing what to do about it aren’t always easy, unless you have already experienced an attack, know what it is and what causes it, and can warn others of your allergy and how to treat it.
If the problem is recognized and properly explained to the person, repeat occurrences can often be prevented. “No one who’s had an anaphylactic episode,” notes one emergency-department chief, “should leave the emergency unit without receiving some information about the condition, guidance for follow-up, referral to an allergist for a thorough assessment, and instructions for emergency action.”
Common Warning Signs of Anaphylaxis Any combination of the following:
- Hives (red, raised skin weals)
- Itching (of armpits, groin, or any part of the body)
- Swelling (of throat, tongue, or any body part)
- Throat tightness or closing
- Difficulty swallowing
- Difficulty breathing
- Red, watery eyes
- Runny nose, sneezing
- Face flushing
- Vomiting, diarrhea, stomach cramps
- Changed voice
- Altered color
- Irregular heartbeat
- Sense of impending doom
- Drop in blood pressure
- Fainting or prolonged unconsciousness
Note: All or some symptoms can occur at the same time.
What are the “Late Phase After-Effects” of Anaphylaxis? Click the link
A note on terminology
The medication used to treat — and perhaps save the lives of — people who suffer anaphylactic reactions is epinephrine, also known as adrenalin. This substance immediately counteracts the dangerous effects of anaphylaxis: it widens constricted airways, stops blood-vessel leakiness (raising blood pressure) and speeds up the heartbeat. Extracted from animal sources, or made synthetically, epinephrine resembles the hormone adrenalin made by our adrenal glands. Sometimes the terms “adrenalin” and “epinephrine” are used interchangeably.