Anaphylaxis is a severe and potentially life-threatening reaction to a trigger such as an allergy. Anaphylaxis usually develops suddenly and gets worse very quickly. It's also known as anaphylactic shock. An allergic reaction is caused by your body’s immune system over-reacting to the presence of a foreign body. It responds to something harmless as if it is a threat. Your body may be so sensitive that tiny quantities of the allergen can cause a reaction. Your body releases chemical substances, including histamine, from cells in the blood and tissues where they are stored. This happens when the allergic sort of antibodies (IgE) react with the foreign body (allergen). The chemicals act on your blood vessels to cause swelling and low blood pressure, and on your lungs to cause asthma. When you have an anaphylactic shock, your blood vessels leak, bronchial tissues swell and blood pressure drops, causing you to choke and collapse.
Anaphylaxis symptoms usually occur within minutes of exposure to an allergen. Sometimes, however, it can occur a half-hour or longer after exposure. Signs and symptoms include:
- Skin reactions, including hives and itching and flushed or pale skin
- Low blood pressure (hypotension)
- Constriction of your airways and a swollen tongue or throat, which can cause wheezing and trouble breathing
- A weak and rapid pulse
- Nausea, vomiting or diarrhea
- Dizziness or fainting
- Feeling lightheaded or faint
- Breathing difficulties – such as fast, shallow breathing
- A fast heartbeat
- Clammy skin
- Confusion and anxiety
- Collapsing or losing consciousness
There may also be other allergy symptoms, including an itchy, raised rash (hives), feeling or being sick, swelling (angioedema), or stomach pain.
Anaphylaxis is a medical emergency. It can be very serious if not treated quickly. Seek emergency medical help if you, your child or someone else you're with has a severe allergic reaction. Don't wait to see if the symptoms go away.
If someone has symptoms of anaphylaxis, you should:
- Call for an ambulance immediately – mention that you think the person has anaphylaxis
- Remove any trigger if possible – for example, carefully remove any wasp or bee sting stuck in the skin
- Lie the person down flat – unless they're unconscious, pregnant or having breathing difficulties
- Use an adrenaline auto-injector if the person has one – but make sure you know how to use it correctly first
- Give another injection after 5-15 minutes if the symptoms don't improve and a second auto-injector is available
If you're having an anaphylactic reaction, you can follow these steps yourself if you feel able to.