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Allergy diagnosis: case history and physical examination

Sue Cross
RN BSc(Hons)
International Project Manager
Respiratory Education Resource Centres
University Hospital Aintree

A detailed clinical history is vital for diagnosing allergy. This requires experience, time and patience. Patients should be allowed to give their own account of their symptoms in their own time, but the questions asked should be structured, focusing on the patient's history (with particular emphasis on previous allergic diseases such as childhood eczema, hayfever and asthma). Frequency, severity, duration and seasonality of symptoms should be ascertained, with particular reference to triggering factors, life-threatening events, and effects of avoidance measures. Other specific areas that should be discussed are:

  • Diet, such as food exclusion and intolerance to aspirin, colourings and preservatives.
  • Family history.
  • Home, work and outdoor environmental risk factors.
  • Treatments they are currently using, particularly antihistamines, topical and oral corticosteroids, and adrenaline autoinjectors.

The age of the patient is important to consider, as Table 1 shows. There are also environmental factors predisposing to development and triggering of allergy (see Table 2).



Presentation and examination

Summer hayfever (allergic rhinitis)
Presentation Seasonal itching, sneezing, watery discharge and associated eye problems.
Examination  The nose may be examined with an auroscope to exclude a structural problem.

Perennial rhinitis
Presentation  Rare, sinister causes for rhinitis need to be excluded. Unilateral symptoms should always be regarded with suspicion, particularly if associated with symptoms of increasing nasal obstruction, bloodstained nasal discharge or facial pain.
Examination Ear, nose and throat surgeons examine the nose with a head mirror and a nasal speculum, but increasingly this is supplemented by rigid or flexible nasendoscopy. In general practice, the nose can be examined with an auroscope fitted with the largest speculum.

(It is easy to confuse a large, swollen, oedematous inferior or middle turbinate with a polyp; polyps, however, unlike turbinates, are usually pale grey, translucent and mobile, and lack any sensitisation of gentle probing.)

Allergic eye disease
Presentation  The symptoms, which usually occur in spring or early summer, are itching, watering, stickiness and difficulty with opening the eyes on awakening. With all these symptoms, blurring of the vision can be present. A stringy mucous exudate is often present on the eye and under the lids.
Examination Eversion of the upper eyelid will often result in exposure of a cobblestone appearance of the upper tarsus.

Allergic asthma
Presentation Symptoms of cough, wheeze, shortness of breath or chest tightness.
Examination  An expiratory wheeze is present in uncontrolled asthma with auscultation. Diagnosis is confirmed with peak expiratory flow rate or spirometry tests:

  • Exercise testing.
  • Serial peak flow measurements.
  • Reversibility testing.
  • Steroid trial.
  • Positive skin prick tests or blood tests can demonstrate causative trigger.

Contact and atopic dermatitis
Presentation  After re-exposure to a sensitiser, an itchy erythematous rash starts to develop within 6-12 hours at the site of contact. The reaction progresses and reaches a peak between 48 and 72 hours after contact. Sensitivity may range from weak to strong-strongly sensitised people may need very little contact to evoke an acute, weeping eczematous reaction. By covering the back of clothing studs with fabric, the nickel in the studs can be prevented from direct contact with the skin.

British Allergy Foundation
Allergy Diagnostic Centre