Body’s immune system produces antibodies that defend against foreign substances. This is good when a foreign substance is harmful, such as certain bacteria or viruses. But some people's immune systems overreact to substances that don't normally cause an allergic reaction.
Allergy symptoms aren't usually life-threatening, but a severe allergic reaction can lead to anaphylaxis. Even if you or your child has had only a mild anaphylactic reaction in the past, there's a risk of more severe anaphylaxis after another exposure to the allergy-causing substance.
The most common causes of anaphylactic shock are:
- Tree nuts such as almonds, walnuts, cashews, brazil nuts
- Dairy products
- Wasp or bee stings
- Natural latex (rubber)
- Penicillin and other drugs
Severe allergic reactions to fresh fruit, such as kiwis and apples, are increasing. In some people, exercise can trigger a reaction – either on its own, or combined with other factors such as eating a certain food. ‘Idiopathic anaphylaxis’ has no obvious trigger.
There aren't many known risk factors for anaphylaxis, but some things that might increase your risk include:
Previous anaphylaxis. If you've had anaphylaxis once, your risk of having this serious reaction increases. Future reactions might be more severe than the first reaction.
Allergies or asthma. People who have either condition are at increased risk of having anaphylaxis.
Certain other conditions. These include heart disease and an abnormal accumulation of a certain type of white blood cell (mastocytosis)