An allergy typically produces a range of symptoms, such as a runny nose; nasal congestion; wheezing or shortness of breath; sneezing; sinus pain; rash or itchy skin, and red, itchy and watery eyes. If a person is allergic to something they have touched or worn, they are more likely to have symptoms that affect the skin (e.g. a rash). While vomiting and swollen lips and tongue can occur after a food allergy.

In severe cases, an allergy may trigger anaphylaxis. This affects the whole body, and in its most serious form €“ anaphylactic shock €“ it can be fatal. Symptoms of anaphylaxis are not always the same, but may include swelling of the throat and mouth, an altered heart rate, flushing of the skin, urticaria (hives), severe asthma, abdominal pain, nausea, vomiting, collapsing and unconsciousness.