The most common allergens that can cause anaphylaxis are foods such as peanuts, tree nuts, milk, eggs, shellfish, fish and sesame seeds, although many other foods have been known to trigger it. Some people react even to tiny amounts of food.
Other causes include wasp or bee stings, latex (natural rubber latex) and medicines. In some people, exercise can trigger anaphylaxis – either on its own or if you exercise around the same time you’re exposed to other allergens.
Sometimes people have a reaction and the cause can’t be found. This is called ‘idiopathic anaphylaxis’, which means the cause is unknown.