Anaphylaxis

The most dangerous allergic reaction is anaphylaxis, which can be a life-threatening emergency.  Anaphylaxis can be triggered by foods, drugs, injections, insect stings and exertion. After taking a drug, eating food, or being stung by a wasp or bee a person may  itch, flush, swell, have trouble breathing, panic and collapse. The foods most commonly associated with anaphylaxis are cow's milk, eggs, wheat, shrimp, fish, peanuts and other nuts. The drugs most commonly associated include penicillin, aspirin, anti-arthritic drugs, morphine, radiocontrast dyes, and anesthetics.

A woman in her late 20's described the following anaphylactic reaction:

"My teeth started tingling and the inside of my throat was itchy...my palms got red and swollen. I felt light-headed and agitated. My heart started to race...by the time I got to the emergency my entire body had broken out in a rash and my feet were so swollen my boots wouldn't come off. But things got worse as soon as I walked in...I couldn't breathe and I began to panic. I felt I was going to die. The doctor in charge was very short with me. He told me to get a hold of myself, that I was just making things worse, but I was out of control. I was terrified and wanted to pass out but couldn't."

Many by-standers and even physicians do not appreciate the gravity of the allergic crisis. Immediate treatment with injected adrenalin, antihistamine, steroids and life support may be necessary to rescue the anaphylaxis victim. The second, late phase of anaphylaxis can develop into a prolonged illness if left untreated. The initial immune response recruits other immune responses. Anaphylaxis is unpredictable and is not caused by a single mechanism. Lethal events include:

1.  tongue and throat swelling, obstructing the upper airway

2.  severe asthma and/or lung swelling with failure of respiration

3.  shock caused by sudden movement of water from blood into tissue spaces (edema)

4.  heart rhythm abnormalities and cardiac arrest

Sudden death occurs rarely and randomly as a tragic consequence of eating a reactive food, often in a restaurant. The actual trigger for anaphylaxis is seldom known with any certainty, although often a single agent such as traces of peanut oil in a salad or dessert may be blamed. Previous occurrences of severe asthma attacks, whole-body hives, local swelling reactions of the tongue, throat, and face; general swelling of the extremities and sudden onset of breathing difficulty suggest increased risk of life-threatening anaphylaxis.

Reports of fatal anaphylaxis are rare and there is a conspicuous absence of systematic studies of the phenomenon.

Sampson et al reported on 13 children and adolescents with fatal and near-fatal food anaphylaxis. All 13 had asthma with previous serious reactions to foods - peanuts (4), nuts (6), cows milk (2), and egg (1). The six patients who died had itching or tingling in the mouth, tightness of the throat, irritability, abdominal pain or vomiting within 3 to 30 minutes of eating the food.  None of the fatalities had self-injected epinephrine. All of the survivors received epinephrine within 30 minutes of the onset of symptoms. Anaphylaxis was rapidly progressive and uniphasic in 7 patients and biphasic in 3 who had early oral and abdominal symptoms followed by a 1-2 hour remission, followed by increasing respiratory symptoms, hypotension and death. Three children who survived had a protracted course requiring ventilatory support and treatment with vasopressors for 3 to 21 days after the onset.

This report emphasizes the potential severity of food reactions and the importance of prompt administration of epinephrine.   The authors suggested that: " Factors believed to have contributed to the fatal outcome included the patients' denial of symptoms, reliance on antihistamines alone for treatment, and failure to administer epinephrine (adrenalin) immediately." All the children in the study had asthma as part of their allergic pattern. Typical symptoms of a a major reaction were itching and swelling sensation of the lips, mouth and tongue, followed by nausea, stomach cramping, vomiting, hives and difficulty breathing.

Anaphylaxis can be triggered by exertion after eating certain foods and may be responsible for sudden deaths in healthy athletes as well as people with known asthma and food allergy who exercise with unaccustomed vigor. Allergy patients are cautioned to exercise in gradually graded increments, watch food intake before athletic events, and avoid sudden, unaccustomed exertion. In one patient wheat was the sensitizing food, and anaphylaxis began with exertion 40 minutes following ingestion. His reactive pattern began with itching during exertion, followed by hand swelling, and generalized redness, and then hives broke out. He experienced drowsiness and shortness of breath. Within minutes he would lose consciousness. Studies of this pattern of reactivity showed elevated blood levels of histamine and an increase in blood acidity. The oral intake of sodium bicarbonate (3.0 grams) taken before exertion was successful in blocking this severe reactivity.

Anaphylaxis Lottery

We can view an anaphylactic attack not just as a single dramatic event but as an avalanche in a series of allergic calamities that stretch out over time. A major event may follow many lesser reactions that stretch out months or years in advance. Sometimes, an anaphylactic reaction heralds the onset of prolonged hypersensitivity, a chronic illness. A severe reaction to an antibiotic, an intravenous dye used in X-Ray studies, and reactions to foods may herald the onset of chronic hypersensitivity. Occasionally, a specific target organ is the focus of anaphylactic damage—the lungs in anaphylactic pneumonia, the thyroid in a patient reacting to an X-Ray dye containing iodine, the brain in a patient who reacted to prawns, or the GIT in a patient reacting to an antibiotic.

Little Anaphylaxis- Panic Attacks

Anaphylaxis can occur at a lower intensity and recur at frequent intervals—frightening, but not life-threatening. While big anaphylaxis leaves you fighting for your life, little anaphylaxis results in milder symptoms, which leave you uncomfortable, anxious, and perhaps a little puzzled. Many people report a recurrent symptom-complex after eating reactive foods with itching, flushing, chest pain and tightness, shortness of breath, sometimes acute abdominal pain or intense headache, and often with anxiety or fear. Alarmingly fast heart action and irregular heart rhythms are also associated. Moderate anaphylaxis may be diagnosed as "panic attacks" because of the fight-and-flight arousal accompanying the immune response. Psychiatrists may prescribe tranquilizers without inquiring about allergenic triggers which are usually foods, drugs, or airborne chemicals. Many food allergic patients end up in the wrong department of the hospital, investigated for heart or neurological problems, or they get trapped in a psychiatric ward under sedation and suspicion.

Management Policy

We have managed several thousand patients with food allergy and no-one has died of anaphylaxis. Minor anaphylactic reactions resolve spontaneously and are common. Since serious reactions are impossible to predict a good protective policy has to balance caution against unreasonable fears. If an allergic person knowingly risks eating reactive foods, some protection might be available with a dose of antihistamine taken before the meal. Antihistamines are more effective as preventive medication than as treatment medications once the allergic reaction is underway.

Intravenous dyes used in X-rays studies are known cause anaphylaxis and it is generally believed that premedication with an antihistamine will prevent this. Normal antihistamines such as benadryl and chlortripalon work and are often included in anaphylaxis kits. Newer non-sedating antihistamines such as claritin will probably work, but there are no studies to prove this. An at-risk person who is traveling or otherwise taking chances by eating foods that may be allergenic may be best to take a daily long-acting antihistamine such as chlortripalon. The drug ketotifen  (Zaditen) may be a god choice for long-term preventive therapy.

Anyone at risk should carry an emergency kit containing injectable adrenalin, antihistamine and oral prednisone and self-administer these drugs as soon as a major reaction begins. This is similar to equipping your home or car with a fire extinguisher - you may never use the kit, but it is available just in case. The easiest way to administer adrenalin is with an auto-injector EpiPen, which is simply pressed into the skin and a measured dose is safely injected. Prednisone is taken orally in the dose range of 20-40 mg after the adrenalin has been injected. Family and friends should know how to administer the emergency drugs. If the drugs are given soon enough, catastrophe can be prevented.

The standard ADULT dose of epinephrine is 0.3 to 0.5 cc of a 1:1000 solution.

Children 0.01 cc/kg up to 0.3 cc; intramuscular injection is preferred in children to speed absorption.

The injections can be repeated twice every 10 to 15 minutes if symptoms persist or worsen. If the first dose was given subcutaneously, the second dose should be given IM to speed absorption. The intravenous route is avoided unless there is shock.

Antihistamine, Benadryl (diphenhydramine)

Adults 50 mg IM or IV:  1.0-2.0 mg/kg for children.

Prednisone 10-40 mg orally  or hydrocortisone  IV  5 mg/kg

If blood pressure drops and does not respond to adrenalin injection, a large bore IV needle is inserted, and infusion of normal saline is begun. Treatment using H1 and H2 blockers, as well as glucocorticoids, can be administered IV .If breathing problems persist, admission to an intensive care unit is required.

When to Act

The problem often is to decide when to push the panic button, use the drugs and rush to the emergency department. Minor to moderate anaphylactic reactions occur at a much higher frequency than the potentially fatal reactions. Many false alarms occur in patients with recurring minor anaphylaxis whose attacks usually resolve with or without treatment. The best idea is to play it safe by administering the blocking drugs with the onset of anaphylactic symptoms. Call an ambulance with the onset of any mouth or throat swelling, difficulty swallowing or serious breathing difficulty. Only skilled medical personnel can treat airway obstruction and shock. Patients with recurrent anaphylaxis, especially where the cause is difficult to determine, can be helped with a prolonged, preventive course of daily prednisone and antihistamine.