Anaphylaxis

What Is Anaphylaxis?

Anaphylaxis is an allergic reaction, while anaphylactic shock is a severe potentially fatal allergic reaction. Experts say that between 1% to 15% of the US population is at risk of having an anaphylactic reaction if exposed to at least one allergen - they add that these figures vary according to various definitions of a reaction. Approximately 1% of those with anaphylaxis may consequently die. UK health authorities say up to 0.05 per 100,000 people may die from anaphylactic shock annually, about ten to twenty cases per year.

The medical term comes from the Greek word ana (against) and phylaxis (protection).

In the UK and USA, the numbers of hospitalizations due to anaphylaxis have been increasing over the last couple of decades. The NHS (National Health Service), UK, says that rates tripled between 1994 and 2004.

When anaphylaxis occurs, the body reacts badly to an allergen, which could be some kind of food, insect bite, venom, or medication. The body treats the substance as it would a harmful bacterium or virus - a threat to health. The reaction may occur straight away, or within hours. In very rare cases, the patient may react days after coming into contact with the allergen(s).

When an allergen gets into a susceptible individual, massive amounts of histamine and some other chemicals are released into the bloodstream. Histamine triggers an inflammatory response which is part of the immune response to foreign pathogens. It causes:

• Dilation of blood vessels, which can result in a sudden drop in blood pressure and narrowing of airways
• Leaking of blood vessels which leads to edema (swelling) in surrounding tissue. When blood vessels leak blood pressure drops

If signs or symptoms are more than mild, the individual should receive medical help as soon as possible. The patient may be given an adrenalin injection, and another one within about ten minutes if there is no improvement. In some cases antihistamines and steroids may be administered.

An individual with an anaphylactic reaction may experience dizziness and malaise. If blood pressure drops suddenly they can pass out. There may be breathing difficulties and wheezing if the airways become constricted. The following signs and symptoms may also be present:

• An unusual, perhaps metallic taste in the mouth
• Diarrhea
• Fainting
• Fever
• Heightened apprehension and anxiety
• Hives
• Itching, which may become severe
• Itchy eyes, which can become red
• Nausea
• Pain in the abdomen
• The heart rate may change
• There may be swelling of the feet, hands, lips, eyes, and even genitals
• Vomiting

Severe breathing difficulties and/or a serious drop in blood pressure can cause shock and lead to death.

What are the treatment options for anaphylaxis?

According to the NHS, UK, if you witness severe symptoms you should call for an ambulance immediately and tell the operator that the patient has anaphylaxis. If you can, remove the allergen.

If the individual has breathing problems try to sit them up. If they experience a drop in blood pressure, lie them down flat on the ground and raise their legs - make sure they are able to breathe if they have fainted. Then place the patient in the recovery position.

Epinephrine (adrenaline injection) - this is administered as soon as possible if the medical team believes the patient has anaphylaxis. Some people carry an adrenaline injection kit. Try to get them to inject themselves, and help them do it if you know how.

If the patient does not respond to the adrenaline injection within about ten minutes, a second one is given. In the vast majority of cases they respond well to this treatment and signs and symptoms subside rapidly.

If you don't feel a pulse, or breathing stops completely, CPR (cardiopulmonary resuscitation) should be performed.

After administering adrenaline, there is a risk that symptoms may come back. So, in most cases the patient is kept under observation in hospital for about 24 hours.

Depending on the severity of symptoms, the doctor may administer corticosteroid or antihistamine injections, usually when they are not severe.

The NHS says that all cases, even mild ones of anaphylaxis should be treated as medical emergencies.

People who are prone to allergic reactions should have an allergy action plan, which may include carrying epinephrine auto-injectors, liaising with schools and employers, and carrying a medical alert bracelet.