Symptoms of an allergic reaction may depend on where the allergen enters your body. An airborne allergen such as pollen, for example, is breathed in through the nose and usually causes symptoms in the nose, eyes, sinuses and throat, such as allergic rhinitis — commonly known as hay fever.
Food allergy, on the other hand, is more often associated with stomach or bowel problems and may cause hives. Allergic reactions can involve several parts of the body at the same time.
The symptoms of allergic reactions range from mild to severe to life threatening. They can be categorised according to the organs affected, which are:
• The skin: hives, eczema and facial swelling
• The respiratory system: symptoms can affect the nose (hay fever), throat (swelling) and lungs (cough, wheeze, bronchospasm)
• The gastrointestinal system: nausea, vomiting, stomach pains and diarrhea
• The cardiovascular system: feeling faint, weakness, pallor, floppiness (particularly in infants), and collapse.
Allergic symptoms may only occur locally — for example localised swelling to a bee sting — or they can be generalised (widespread).
An anaphylactic reaction is where a generalised allergic reaction affects the respiratory and/or cardiovascular systems, as well as the skin and/or gastrointestinal tract.