Diagnosing Allergies
Diagnosis is suggested by the clinical history. Consider the following symptoms:
Immediate allergic reaction | Delayed allergic reaction | Not allergy | |
Skin | urticaria, angioedema | eczema flare | rashes which are not itchy, rashes associated with bruising |
Gut | nausea, vomiting, diarrhoea | vomiting, colic, diarrhoea (sometimes with blood) | watery diarrhoea with flatus only may suggest lactose intolerance |
Respiratory tract | cough, stridor, drooling, wheeze, dyspnoea | asthma attack | choking on foods, cough productive of purulent sputum |
Circulation | faintness, loss of consciousness | palpitations |
Skin prick and blood allergy tests provide supportive evidence for immediate, but not delayed reactions. Both tests can result in false negative and positive results. Where there is doubt a supervised challenge to the allergen is recommended.
More information on skin prick and blood testing can be found in the Resource: Patient leaflet section.