What is Anaphylaxis?

Anaphylaxis is a severe allergic reaction - the end of the allergic spectrum. The whole body is affected, usually within minutes of exposure to the allergen but sometimes after hours. Causes include food, insect stings and drugs.

What are the symptoms?

• Swelling of throat and mouth
• difficulty in swallowing or speaking
• alterations in heart rate
• difficulty breathing - due to severe asthma or throat swelling
• hives anywhere on the body, especially large hives
• generalised flushing of the skin
• abdominal cramps, nausea and vomiting
• sudden feeling of weakness (drop in blood pressure)
• Sense of impending doom
• collapse and unconsciousness

Nobody would necessarily experience all of these symptoms. Some people find that the symptoms they experience are always mild. For example, there may be a tingling or itching in the mouth - nothing more. This is not serious in itself, and may be treated with oral antihistamines. Nevertheless, it is wise in all cases to make an appointment with the doctor and seek a referral to a specialist allergy clinic.

If there is marked difficulty in breathing or swallowing, and/or sudden weakness or floppiness, regard these as acute symptoms requiring immediate treatment.

What is the treatment?

An adrenaline injection must be given, as directed, as soon as a severe reaction is suspected. Call an ambulance. If there is no improvement in five minutes, give a second injection. Anti-histamines and a hydrocortisone injection can be given, if available, but adrenaline (also named epinephrine) is the first line of defense.

Why does anaphylactic shock occur?

Any allergic reaction, including the most extreme form, anaphylactic shock, occurs because the body’s immune system overreacts in response to the presence of a foreign body, which it wrongly perceives as a threat.

What exactly is going on?

An anaphylactic reaction is caused by the sudden release of chemical substances, including histamine, from cells in the blood and tissues where they are stored. The release is triggered by the reaction between the allergic sort of antibodies (IgE) with the substance (allergen) causing the anaphylactic reaction. This mechanism is so sensitive that unbelievably small quantities of the allergen can cause a reaction. The released chemicals act on blood vessels to cause the swelling and low blood pressure, and in the lungs to cause asthma.

Why does adrenaline work?

In anaphylactic shock, blood vessels leak, bronchial tissues swell and blood pressure drops, causing choking and collapse. Adrenaline (epinephrine) acts quickly to constrict blood vessels, relax smooth muscles in the lungs to improve breathing, stimulate the heartbeat and help to stop swelling around the face and lips (angioedema).

How do I know if I am at risk from anaphylactic shock?

If you have suffered an adverse allergic reaction in the past, then any future reaction may also be severe. You should see your GP and insist on a referral to a specialist allergy clinic. If you have asthma as well as allergies, a referral is of particular importance. Your GP should have an NHS allergy clinic handbook, approved by the British Society for Allergy and Clinical Immunology. Where nuts and seeds are concerned, even mild symptoms should be regarded as possible warning signs. Again, an assessment by a specialist is vital. Allergic reactions are unpredictable and may vary in severity from one time to the next.

What are the most common causes of anaphylactic shock?

Among the most common causes are: peanuts; nuts; sesame; fish; shellfish; dairy products; eggs; wasp or bee stings; natural latex (rubber); penicillin or any drug or injection. Severe allergic reactions to fresh fruit are also sometimes reported. In some individuals, exercise can trigger a response - either on its own or in combination with other factors such as ingestion of a particular food.

How can the specialist know how allergic I am?

The honest answer is that he cannot be sure. There is, as yet, no perfect way of measuring an individual’s potential for a severe allergic response. It is even more difficult in young children. However, the consultant can do several things that will provide valuable clues.

History: The Specialist will take a detailed history of previous reactions and other allergic conditions you may have: such as hay fever, rhinitis (A runny nose), eczema; and especially asthma. If you are asthmatic, the specialist will want to know how severe it is and how well you manage it. The specialist may also perform a physical examination. It is important to tell the practitioner if you are taking any medication.

Skin prick tests: Small amounts of the suspected allergens are inserted into a series of shallow pin-pricks on the arm or back. If you are allergic, say, to egg, the site of that pinprick will develop a red wheal and flare within 15 minutes. The size of the wheal and flare gives some idea of the degree of your reactivity to that particular allergen. Skin prick tests for food allergies appear to be slightly less reliable than for other allergies, and false negatives can occur.

Blood tests: R.A.S.T. (radioallergosorbent) or Cap assay tests involve taking a small sample of blood. They indicate the degree of reactivity to a particular substance. However, they are more expensive and time-consuming, and the results do not always reflect the real life situation.

How can I avoid anaphylactic shock?

1. Minimize the risk. Be vigilant about exposure to the allergen. If you are food allergic, read labels like Sherlock Holmes: look for the “hidden” allergen. You can easily recognize a packet of peanuts but may miss the word “groundnuts” on the side of a tin of curry sauce. If you are wasp or bee allergic, do not wear bright or shiny clothing or accessories while outdoors, and use an insect repellent containing diethyl-m-toluamide.

2. Be assertive about asking for detailed information about foods from manufacturers and restaurants. The more we ask, the more they will understand the importance of accurate, complete ingredient lists.

3. Be particularly careful in restaurants, where proprietors are under no obligation to list ingredients. Question staff very directly. It may be necessary to speak with a senior manager. Remember that staff may not be fluent in English, or the chef may be exceptionally creative and may like to throw in a handful of something extra for flavor or texture. Fast food chains, like Macdonald’s, have stricter quality control than the corner takeaway and may have ingredient lists available for you to check.
4. Be alert to all symptoms! Don’t kid yourself - denial of the symptoms is foolish. Reach for the adrenaline (epinephrine) if you think you are beginning to show the signs of a severe reaction. Do not wait until you are sure. Even if adrenaline is administered, you will still need to get to the hospital as soon as possible. Call an ambulance.

5. Make sure you are completely comfortable with both the adrenaline kit and the method of administration that has been prescribed for you. If you are hesitant about it, ask for a different kind of adrenaline kit and make sure everyone in your family knows how to administer it - and when. Do not be frightened of adrenaline. The dose you will administer has very few side effects, which will pass quickly in any case. Adrenaline was widely used in asthma attacks before the current generation of drugs was developed. It has been around for a hundred years and is a very reliable and well-understood drug. In rare cases, where there are heart difficulties or where a patient suffers from palpitations, there could be difficulties. If you are likely to be affected in this way, please discuss the issue in detail with your doctor.

6. Develop a crisis plan for how to handle an emergency. Get your allergist or GP to help. Have this written out for family and friends - put it on the bulletin board at home; carry one in your pocket. If a child is a person at risk, make sure his teachers and friends’ parents have a copy - along with the adrenaline. Make sure everyone knows where the adrenaline is when you go out, or when you are at home.

7. Wear a MedicAlert bracelet.

8. Be open about your allergy problem with your family, friends and colleagues. It is easy to avoid a Thai restaurant if everyone knows you are allergic to peanuts.

What should I do if I think I have an anaphylactic reaction?

1. Follow your crisis plan. These are some key points:

Is there a marked difficulty in breathing or swallowing?

2. Is there sudden weakness or floppiness?

3. Is there a steady deterioration?

4. Any of these is a sign of a severe reaction. Administer adrenaline (epinephrine) without delay if you believe the symptoms are acute or becoming serious.

5. Dial 911 or get someone else to do it.