What is Anaphylaxis?

Anaphylaxis is a severe allergic reaction - the extreme end of the allergic spectrum.

The term allergy is used to describe a particular response by the body's immune system to a substance in the environment (including foods). This response occurs in predisposed individuals and results in the development of a particular antibody (IgE) against the substance. The next time the person meets this substance the antibody reaction causes the release of certain chemicals into the body. These chemicals cause the symptoms of the allergic reaction.

In most allergic reactions these chemicals are released locally into the tissues in a particular part of the body (skin, airways, eyes etc). Thus the symptoms of the allergic reaction usually only occur in this area. In anaphylaxis, the chemicals that cause the allergic symptoms (e.g. histamine) are released generally in the bloodstream. This causes symptoms around the whole body, usually within minutes of exposure to the trigger substance (allergen) but sometimes hours later. We do not understand why certain allergic people are affected in this way, rather than with 'normal' allergic reactions.

The most common causes of anaphylactic reactions include certain foods, insect stings and drugs. The most commonly implicated foods are peanuts, tree nuts, eggs, shellfish, milk, fish, eggs and some seeds such as sesame.

Bee and wasp stings are the most common insect triggers.

Antibiotics, anaesthetic drugs, aspirin, ACE inhibitors and injections used in X-ray procedures can cause anaphylaxis or anaphylactic-like symptoms in some people.

What are the symptoms?

Any or all of the following symptoms may be present:

• Swelling of throat and mouth
• Difficulty in swallowing or speaking
• Difficulty in breathing - due to severe wheezing or throat swelling
• Urticaria (hives, nettlerash) anywhere on the body
• Generalised flushing of the skin and itching
• Abdominal cramps, nausea and vomiting
• Sudden feeling of weakness (Drop in blood pressure)
• Collapse and unconsciousness

Treatment

Fortunately most people suffer only mild or moderate symptoms which can be relieved by antihistamines taken at the first sign of a reaction. However these take time to work and in a more severe anaphylactic attack, antihistamines are not an adequate treatment. The first line treatment for severe symptoms is adrenaline (Epinephrine) given by injection into the muscles. Severe symptoms include throat constriction with breathing difficulties, breathlessness or wheeze, or shock (weakness, faintness, collapse, unconsciousness). Adrenaline (Epinephrine) will start working within a few minutes, reducing swelling, relieving wheeze and improving blood pressure. Once adrenaline has been given, antihistamines can be given as well, but the adrenaline should be given first. Adrenaline given in this way is a safe treatment and you should not hesitate to use it if required.

Adrenaline is a short-acting drug and the effects will wear off quite quickly. It is very likely that further treatment will be required, and you should always call an ambulance to take you to hospital if adrenaline (Epinephrine) has been used. Do not wait to see if the symptoms clear up - call an ambulance immediately and state that you are having an anaphylactic attack.

It is better if you lay down as this helps to maintain your blood pressure and avoids injury if you should faint. You may be more comfortable with your shoulders raised a bit if you feel wheezy or short of breath.

Adrenaline injections

These are available on prescription from your GP or specialist.

EPI-PEN AUTO-INJECTOR
ADULT or PAEDIATRIC (EPI-PEN JUNIOR).
A second dose may be required. Shelf life of 18 months.
Alk-Abello (UK) Limited
www.epipen.co.uk
www.alk-abello.co.uk
Tel: 01488 686 016

ANAPEN AUTO-INJECTOR
Anapen 0.3mg solution (adult)
Anapen 0.15mg solution (junior)
A second dose may be required
Shelf life for Anapen 0.3mg solution - 24 Months
Shelf life for Anapen 0.15mg solution - 21 Months
www.anapen.co.uk
Tel: 01722 742900

Remember - if you need one, you need two. You should always have a spare in case you need a second dose, or in case the first one fails to work.

Always call an ambulance if you have used your adrenaline pen.

When used to save life in an emergency, the prescription-only status of adrenaline does not apply.

Updated 4/2009