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 |
Symptoms in red indicate anaphylaxis
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.