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An allergy is an adverse reaction that the body has to a particular food or substance in the environment. Most substances that cause allergies are not harmful and have no effect on people who are not allergic to them. Any substance that triggers an allergic reaction is called an allergen. Common allergens include pollen, house dust mites, mould and pets. Less common allergens include nuts, fruit, or latex. An allergy develops when the body's immune system reacts to an allergen as though it was a threat, like an infection. It produces antibodies to fight off the allergen in a reaction called immune response. Next time the person comes into contact with the allergen, the body remembers the previous exposure and produces more antibodies. This causes a release of chemicals in the body that lead to an allergic reaction.

Common allergic disorders include asthma, eczema and hay fever. Symptoms of an allergy can include sneezing, wheezing, coughing and skin rashes. The nature of the symptom depends on how you came into contact with the allergen. For example, you may experience problems with your airways if you breathe in pollen. Anaphylactic reactions are those that cause a serious reaction that affects the respiratory system, and this can be life-threatening. The allergen could be by ingesting it, by inhaling it, by absorbing through the skin, or an injection, like a bee sting. Allergic reactions are not just anaphylactic types of reaction. They can be different levels of reactions, which include allergies, sensitivity and intolerance.

An allergy is a reaction produced by the body's immune system when it encounters a normally harmless substance. Sensitivity is an exaggeration of a normal side effect produced by contact with the substance. For example, the caffeine in a cup of coffee may cause extreme symptoms such as palpitations and trembling when it would normally only have that effect if taken in very large quantities. Intolerance is where a substance, such as lactose or gluten, causes unpleasant symptoms such as diarrhoea for a variety of reasons but does not involve the immune system. People with an intolerance to certain foods can typically eat a small amount without having any problems. In contrast, people with a food allergy will have a bad reaction even if they come into contact with a tiny amount which they're allergic to. Where someone has an intolerance or sensitivity, treatment is often to remove the source and let nature take its course, but where there's an anaphylactic reaction to an allergen, auto-injectors are often used to inject a preset dose of adrenaline into the muscle of the body, which reduces the effects until emergency help arrives.

Signs and symptoms of an anaphylactic reaction include itchy skin or a raised red rash, swollen eyes, lips, hands and feet, feeling light-headed or faint, narrowing of the airways, which can cause wheezing and breathing difficulties, abdominal pain, nausea and vomiting, and also collapse and unconsciousness. Anaphylaxis should always be treated as a medical emergency. If you suspect that you or someone else is experiencing symptoms of anaphylaxis, you should immediately dial 999 for an ambulance. There are different types of auto-injector. Now, these auto-injectors are prescribed by a doctor. They're not something you can just buy at a chemist. So each individual person would have their own prescription. It may well be that this person has more than one auto-injector, because if the first auto-injector hasn't worked after 10 or 15 minutes, it may be that that person has a second one and therefore they'd have two units because they're all single-dose syringes.