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The NHS National Institute for Health and Clinical Excellence define anaphylaxis as “a severe, life-threatening, generalised or systemic hypersensitivity reaction”. Not everyone has allergies, and not everyone who has allergies will be susceptible to going into anaphylactic shock. Also, just because someone has an allergic reaction does not mean that they will then go on to experience anaphylaxis. The reaction may start suddenly within seconds, or take minutes or even hours to develop following contact with the allergen.

Common food triggers include peanuts and tree nuts, fish and shellfish, citrus fruit, eggs, and dairy products such as milk and cheese. Other allergens include venom from stinging or biting insects, medicines – most commonly antibiotics, aspirin or ibuprofen, or substances such as latex.

Allergic reactions can manifest in many different ways, however anaphylaxis has a few common signs and symptoms, one of the most common being breathing difficulties. This is because all of the small tubes in the lungs which deliver oxygen swell up, and consequently the person cannot get enough oxygen into their body. If this happens, they will be breathing very quickly but each breath will be very shallow. Anaphylaxis can also cause a drop in the person’s blood pressure which may make them faint or even go unconscious.

This is also the body’s response to not receiving enough oxygen. This is because fainting normally makes the person fall to the floor, which in turn makes it easier for blood to get back to the head, and also puts a bit less strain on the heart and lungs. Other signs and symptoms of an allergic reaction include a rapid heartbeat, cold clammy skin, confusion or nausea. It is worth mentioning that the more serious the reaction, the more seriously these signs and symptoms will present.