Clinical review

Allergy in general practice

Sue Cross,  Sallie Buck,  Jane Hubbard. 

In parallel with the known increases in atopy (confirmed by a positive response in skin prick testing to one or more common allergens) and allergy there has been a marked increase in the proportion of general practitioner consultations for asthma, hay fever, and eczema. A greater awareness of the importance of allergy should lead to better diagnosis and management of allergy. This is essential for perennial allergic asthma in children and adults, in whom environmental control and allergen avoidance measures directed against house dust mites are of proved value in reducing asthma symptoms and bronchial hyperresponsiveness. It seems likely that these factors also reduce the need for drug treatment.

View larger version (92K): [in this window] [in a new window]   House dust mite, the major cause of perennial allergy in Britain

Rhinitis symptoms commonly have an allergic aetiology and may be seasonal or perennial. They may be responsible for severe impairment of quality of life. Rhinitis symptoms are frequently trivialised and misdiagnosed by both patients and doctors as "the permanent cold." This is unfortunate as avoidance measures combined with either topical corticosteroids or antihistamines, or both, are extremely effective in controlling symptoms with minimal side effects. Recent surveys have suggested that up to 80% of people with asthma also have rhinitis; treating rhinitis in such people has been shown to reduce asthma symptoms and bronchial hyperresponsiveness.

	Role of the practice nurse

The practice nurse has a major (and now established) role in the routine care of asthmatic patients in general practice. It seems logical that this role of the specially trained nurse could be extended, with the support of the general practitioner, to include the recognition and treatment of the allergic component of asthma and also rhinitis.

The extent of the nurse's role depends on many factors, including skills, training, and knowledge. The knowledge base and skills of the doctor and the circumstances of the practice will similarly have an impact. Inquiry about allergic triggers in asthma should be routine in any asthma clinic.

An important question is whether this role should be extended to include more detailed inquiry and use of a simple range of skin prick tests. This issue is particularly important in Britain, which, in contrast to Europe and the United States, has few specialist allergy clinics in the NHS. By spending dedicated time with patients, or by enabling the doctor to spend more time with them, the trained nurse has an immense contribution to make to the task of improving management of asthma and allergy.

	Allergy diagnosis in general practice

Accurate allergy diagnosis may be limited by the availability of consultation time. None the less, time taken early on in obtaining a full history may well save time later. Patients should be allowed to explain their symptoms in their own time. At the end of the consultation it is often helpful to ask the patient, "what is your main problem?"

	Skin prick tests

Skin prick testing identifies IgE sensitivity to common allergens, allows diagnosis (or exclusion) of atopy, and provides helpful objective information that should be interpreted in the context of the clinical history of symptoms (or lack of symptoms) on exposure to relevant allergens in the indoor and outdoor environment or workplace. Although skin prick testing with aeroallergens is a simple and safe procedure, it requires training in technique and, more important, in interpretation of the results. Measurement of serum allergen specific IgE, an alternative to skin tests, is done in most district hospitals.

Whether skin prick testing should be performed routinely in general practice in Britain remains a matter of debate. A pilot study evaluated skin prick testing in children and adults in 320 patients in 16 general practices in Britain. The study involved two days' training in allergy, combined with instruction in skin prick testing with four common allergens (and positive and negative controls). The participating nurses found that the techniques were simple, relatively easy to incorporate into their routine assessment of new referrals to the asthma clinic, and acceptable to both adults and children. The nurses also found the techniques acceptable. The procedure undoubtedly increased the nurses' awareness of the role of allergy in patients' asthma, although further studies should look at specific outcome measures. An important finding was the value of negative results of skin prick tests, which excluded atopy in these patients and enabled the investigators to advise patients against inappropriate allergen avoidance measures. A further important advantage was the visual illustration provided by positive results of skin tests, which could be used to reinforce the need for allergen avoidance.

Important practical considerations include the avoidance of use of antihistamines before skin prick testing. In general, when there is concordance between the clinical history and skin prick testing, management is straightforward. For example, an asthmatic patient who has symptoms on exposure to cats or dust and in whom there is an objective confirmation (from skin prick testing) should receive appropriate advice on avoidance. Similarly, a negative history together with negative results of skin prick testing excludes the need for allergen avoidance. When results are discordant (positive history with negative results, or vice versa) they may indicate the need for referral to a specialist. Skin prick tests with common aeroallergens are safe and may be performed by the practice nurse. However, in view of the theoretical risk (albeit remote) associated with giving allergens, injectable adrenaline should be available. Skin prick testing in general practice may be restricted to the four common allergens (house dust mite, cat, dog, grass) and controls (histamine and allergen diluent). Patch testing for suspected contact allergy is complex and should be performed by a specialist dermatologist.

	Management of allergy in general practice

If an allergen has been identified as contributing to or causing disease then consideration should be given to the need for measures for avoiding that allergen. These measures should be regarded as complementary to drug treatment. This should not detract from time given to advising patients on the need to take prophylactic drugs regularlyfor example, regular inhaled corticosteroids for asthma. In practice, total avoidance, especially of aeroallergens, may be very difficult, so the aim is to reduce overall exposure as much as possible.

Avoidance measures for house dust mites should focus mainly on the bedroom. The room should be ventilated regularly; mattresses, pillows, and duvets should be encased in mite proof allergen covers (which may be left in place for up to six months) with the usual bed covers for mattress, pillows, and duvet put on over the top. Patients should be advised to launder this bedding every 1-2 weeks at 60°C. Vacuum cleaners with an adequate filter to remove house dust mite allergen and prevent dissemination through the vacuum exhaust have been recommended by the British Allergy Foundation. Removal of the bedroom carpet (where possible) is important. Soft toys should be reduced to a minimum and be washable; they may be placed regularly in a freezer to kill the mites. Even when these measures are applied conscientiously improvement may take 3-6 months.

When pet allergy is diagnosed, the offending animal (and if possible all furry animals) should be excluded from the home. Psychosocial considerations may mean that the best that can be achieved is confining the animal outside or in the kitchen, with a recommendation not to replace an animal. Again, advice to remove the bedroom carpet should be given. Some studies have shown that washing a cat weekly (cat allergens are present on the fur and are extremely water soluble) may reduce allergen load when combined with removal of the bedroom carpet. Even if the pet is removed, vigorous cleaning for 3-6 months afterwards is required to minimise pet allergen concentrations in the home.

It is unlikely that patients with summer hay fever will be able to avoid pollens. The best aim should be control of symptoms with topical corticosteroids and antihistamines so that the patient may lead as normal a life as possible. Patients with severe hay fever, however, should keep windows shut (cars and buildings); wear glasses or sunglasses; avoid grassy spaces, especially in the evening, when pollen counts are highest; fit a pollen filter to the car; and consider a holiday by the sea or abroad at peak times.

The practice nurse routinely provides individualised written instructions for asthmatic patientsabout drug treatment, need for peak flow monitoring, inhaler technique, etc. He or she may also advise on allergen avoidance and environmental control measures. The nurse may also advise patients with rhinitis how to use nasal sprays: blow the nose; tilt head so the chin is resting on the chest; hold the spray bottle upright and place nozzle just inside one nostril; apply one or two sprays as prescribed; repeat with the other nostril.

View larger version (16K): [in this window] [in a new window]   How to use a nasal spray

Occasionally corticosteroid nasal drops may be required, particularly for rhinosinusitis. These should be taken in the "head upside down position," best achieved by lying on your back on a bed, tilting your head right over the edge of the bed, applying drops to both nostrils and waiting for two minutes before getting up.

A Medic Alert bracelet or necklace (with an inscription that alerts other doctors to the possible cause of any future reaction) is very valuable for people at risk of anaphylaxisfor example, in response to penicillin, stinging insects, foods, or latexand for patients with asthma who have sensitivity to aspirin. The practice nurse may teach patients how to use syringes of injectable adrenaline (epinephrine)usually this will follow recommendation by an allergy specialist.

General practitioners can obtain a list of NHS allergy clinics from the British Society for Allergy and Clinical Immunology.

View larger version (53K): [in this window] [in a new window]   Medic Alert bracelet: important for patients at risk of anaphylaxis

	The way forward

Many primary care practices already benefit from clinics devoted to the management of asthma, one of the common diseases frequently associated with allergy. Taking an allergy history with or without skin prick tests may enhance the effectiveness of asthma care. Skin testing with a limited range of reagents in general practice is both practicable and desirable. The recognition of the importance of rhinitis and the role of allergy in rhinitis and eczema will also enhance the management of atopic patients in general practice. Food allergy and occupational allergy should be considered; if such allergies are present, the patient should be referred to a specialist. The logical person to deliver allergen avoidance advice is the practice nurse, supported by the primary care doctor, and, where necessary, the local allergy service, whether provided by an NHS based specialist allergist or an organ-based specialist with training in allergy. The allergist may also effectively evaluate the role of allergy in patients presenting with non-specific symptomsfor example, the so-called multiple chemical sensitivity syndrome.    

	Acknowledgments

The Medic Alert Foundation provided the picture of the Medic Alert bracelet.    

Sue Cross is director of training at the National Asthma and Respiratory Training Centre, Warwick, and chairwoman of the Nurse Practitioner Association; Sallie Buck and Jane Hubbard are practice nurses in Exeter and Kingston on Thames respectively, and both are regional trainers for the National Asthma and Respiratory Training Centre, Warwick.

The ABC of allergies is edited by Stephen Durham, honorary consultant physician in respiratory medicine at the Royal Brompton Hospital, London. It will be published as a book later in the year.