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Allergies in children: diagnosis and management

Samantha Walker
Director of Research

Annie Wing
Paediatric Module Leader
National Respiratory Training Centre

Allergic diseases such as hayfever and allergic asthma are common, with an estimated 25% of the general population now suffering from some form of allergic condition.(1) In children, the development of allergies follows a defined pattern referred to as "the atopic march". Atopic dermatitis and food sensitivities are more common in infants and younger children, with hayfever (seasonal allergic rhinitis), perennial allergic rhinitis and allergic asthma developing throughout adolescence. For optimal management, it is important to recognise the systemic nature of allergic disease and the likelihood of symptoms manifesting themselves in different (but sometimes multiple) organ systems in the same children over a period of time. This article will discuss the various manifestations of allergic disease in children, their diagnosis and management.

Mechanisms of allergy
Allergic reactions occur as a result of an interaction between an allergen (such as grass pollen or a peanut) and mast cells via an antibody called immunoglobulin E (IgE). The inhalation, ingestion or injection of the allergen releases histamine from mast cells into the local and general circulation, causing the characteristic symptoms of allergy in one or more organ system.
Allergic reactions vary from the sneezing and runny nose seen in summer hayfever to rapid onset of anaphylaxis. The classic signs of allergy include itching, redness and swelling, and its time course (immediate symptoms usually occurring within 15 minutes of exposure) marks the cornerstone of allergy diagnosis. At a simplistic level, this allows the health professional to quickly differentiate between allergic and nonallergic symptoms.

The term "allergy" is currently used to describe an immunological response to common aeroallergens or food/drug allergens. This defines allergy as being quite separate from "intolerance", an example of which is migraine in response to some foods. "Atopy" is described as a hereditary predisposition to develop allergic symptoms and is defined clinically by a positive skin prick test or specific IgE blood test to one or more common aeroallergens. It is important to remember that patients with a positive skin/blood test to a particular allergen may not have symptoms on exposure to that allergen and so a diagnosis of allergy cannot be made by the results of a skin/blood test alone.

Allergy diagnosis
Allergy diagnosis is dependent on taking a detailed clinical history, and, in an ideal world, should be supported by the measurement of specific IgE, either by a skin prick test or by measurement of specific IgE in the peripheral blood. Invasive tests such as these can be distressing for young children and are not commonly used as a diagnostic tool in primary care.
Successful management of allergic symptoms does not depend on identification of an allergic trigger (exceptions include food and drug allergies) but on appropriate pharmacotherapy. Appropriate pharmacotherapy will in turn depend on the recognition of allergy and nonallergy symptoms and it is therefore important to differentiate between allergic and nonallergic conditions as management strategies may differ.

Allergic skin diseases

Atopic dermatitis (eczema) is an allergic skin disorder that commonly manifests itself in the first year of life. It is often the first indication of atopy in infants and is characterised by extreme itchiness due to dry, scaling skin. Triggers include food allergens and aeroallergens. The most common food allergens are eggs, peanuts, milk, soya, wheat and fish, which account for nearly 90% of the foods that exacerbate dermatitis.(2,3) Dermatitis caused by common foods such as egg and milk are much more prevalent in babies and young children, although aeroallergens such as pollens, house dust mites and animal dander can also exacerbate the condition. A careful history can help to identify allergens present in the diet or environment that are triggering the dermatitis.
Management involves the removal or avoidance of any exacerbating factors such as infection, irritants and allergens where possible. Emollients are used to restore and maintain skin hydration as well as agents to reduce inflammation, such as topical steroids. Topical steroids should be applied when dermatitis is active (ie, when skin is red and itchy), the aim being to use the weakest possible steroid to control the disease. The negative impact of atopic dermatitis on the child and family is associated with many quality-of-life issues such as sleep disturbance, low self-esteem and lack of confidence.(4,5)

Urticaria and angioedema
Urticaria presents as whealing and erythema of the skin. It looks like a nettle rash or hives and is usually profoundly itchy. It is relatively common, with 20% of the population estimated to have at least one episode in their lifetime. Angioedema is a deeper tissue swelling resulting from oedema in the dermis and subcutaneous tissues or the mucous membranes.
Acute urticaria (lasting less than 6 weeks) and angioedema are often allergic in origin and commonly occur as a result of exposure to foods (eg, peanuts, eggs, shellfish and milk), drugs (eg, penicillin) and insect bites. Chronic symptoms, lasting for more than 6 weeks, are rare (around 0.1% of the population). Approximately 95% of cases remain idiopathic, and IgE-mediated hypersensitivity is not usually associated (although it is widely held to be by patients and doctors alike). Treatment involves avoidance (where a clear trigger is identifiable), together with nonsedating antihistamines.

Allergic rhinitis (hayfever)
Symptoms of allergic rhinitis include itching, sneezing, watery rhinorrhoea (runny nose), itchy eyes and nasal blockage. It is very common, its prevalence ranging between 15 and 30% depending on age, and is a particular problem in young children and adolescents, where symptoms may lead to sleep disturbance, activity limitations and emotional problems.(6) Trigger factors include grass and tree pollens, house dust mites and moulds, most of which are ubiquitous in the UK and largely unavoidable. Management depends on avoidance (where possible) and the regular administration of appropriate pharmacotherapy. Pollen avoidance is difficult and house dust mite avoidance almost impossible. It is noteworthy that there is no evidence of clinical efficacy for house dust mite avoidance in adult studies.(7)
Symptoms usually respond to a combination of a daily topical nasal steroid and a nonsedating antihistamine. Prescription of a topical nasal steroid should always be accompanied by an explanation of device technique according to the manufacturer's instructions. Patients should be followed up 2 weeks after the onset of symptoms. First-generation antihistamines (eg, chlorpheniramine) should be avoided because treatment with a sedating antihistamine can further compound the disruptive effects of rhinitis.(8)

Allergic asthma
It has been observed that allergic rhinitis and asthma often coexist in the same patients, and recent guidelines have emphasised the importance of treating allergic rhinitis as well as asthma in such patients.(9,10) Allergic triggers are common in children and can usually be identified from a good clinical history. Management is based on avoidance (where possible) and pharmacotherapy, preferably via the inhaled route according to the BTS/SIGN guideline for asthma.(11)

Food allergy/intolerance
Adverse reactions to foods can largely be divided into those known to have an IgE-mediated mechanism and those caused by nonallergic mechanisms. The challenge for the health professional is to distinguish between the two! This can be difficult but is necessary if appropriate treatment and avoidance is to be given.
Food allergy is a common manifestation of atopy in children, affecting up to 8% of children under 3,(12) but only 2% of the adult population.(13) Some will "grow out of" their allergy with time, but this is less common in those allergic to peanuts, fish and shellfish. Around 10% of children with asthma and 30% of those with atopic dermatitis have an adverse reaction to food. Despite parental perceptions, relatively few foods cause food allergy. In fact nearly 90% of food allergies are caused by common foods such as milk, eggs or wheat.
Diagnosis depends on a careful history and the performance of skin pricks/IgE tests to suspected allergens. Food diaries may be helpful to eliminate food triggers. The only long-term treatment for food allergy and intolerance is to avoid the food. Children in whom food allergy is suspected, particularly those who have had a reaction involving throat swelling, tongue swelling and/or wheezing and who also have asthma, should be referred to an allergy specialist or paediatrician.

Anaphylaxis is the term used to describe the severe IgE-mediated reaction that occurs following exposure to the relevant allergen in previously sensitised individuals. Common allergic triggers include peanuts, penicillin, insect venom and shellfish; nonallergic triggers include radiocontrast media and drugs used in general anaesthesia. Anaphylaxis is relatively rare, although it is the most frightening manifestation of IgE-mediated allergy. This is because the reaction develops rapidly, is systemic and is potentially fatal. In addition, it can be triggered by minute quantities of the relevant substance, so that children and their parents can become extremely anxious about the possibility of anaphylaxis developing unexpectedly.
Anaphylaxis is a medical emergency, and a good outcome depends on its rapid recognition and appropriate treatment. Recent guidelines recommend early use of adrenaline in patients with a severe allergic-type reaction with respiratory difficulty and/or hypotension, particularly if there are skin changes present.(14) Long-term management should include urgent referral to a paediatric allergy specialist for diagnosis and risk assessment. As with all allergies, avoidance is an important part of management. Children may find it reassuring to wear a bracelet or necklace giving details that will alert healthcare personnel of the cause of the reaction and recommended treatment. Details of self-help groups such as the Anaphylaxis Campaign (see Resources) may also be helpful.

Allergic diseases can affect multiple organ systems within individuals over time. It is therefore important to ask children who present with one allergy symptom about the presence of others and treat them appropriately. Diagnostic and management guidelines are available for the majority of allergic conditions, and health professionals should be familiar with their contents. One of the difficulties in allergy management is the lack of trained specialists. Recent government initiatives may offer a solution in terms of training more allergists, developing regional allergy services and encouraging training for practice nurses and general practitioners at the primary care level.


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National Respiratory Training Centre
Anaphylaxis Campaign