Allergy testing in paediatric atopic dermatitits

A topic dermatitis (AD) is a common affliction of children and both its diagnosis and management provide concerns for patients and their medical advisors. Children with AD often have other atopic (immunoglobulin E [IgE]-mediated) disorders, such as asthma, food allergies and allergic rhinitis.1 AD is also often referred to as ‘eczema’; although AD is technically a subtype of eczema, in common practice the terms are used interchangeably. Allergic contact dermatitis, however, is different to AD, usually manifesting within days (rather than minutes or hours) of exposure in areas of skin directly in contact with the allergen. The clinical manifestations of AD are skin changes characterised by erythema, scaling, weeping and pruritus. The distribution of skin lesions in AD varies with the patient’s age: typically infantile AD involves the face, scalp, arms and legs, whereas in older children lesions are often prominent on flexor surfaces of the extremities.2 Onset of AD is primarily before the age of 5 years, and often before 1 year of age. The impact of this condition can be severe, particularly because of the accompanying intense pruritus, which often has a significant impact on a child’s functional ability and can cause major sleep disturbance.3 The consequences of AD are not limited to the child as family members also suffer major effects and incur significant personal and financial costs.4 The aetiology of AD is related to an underlying defective skin barrier with altered immune responses to environmental allergens, skin irritants and micro-organisms.5 Multiple genetic abnormalities have been identified in patients with AD, with most evidence linking AD with a mutation in the FLG gene, which encodes for filaggrin (derived from ‘filamentaggregating protein’).1,6 Filaggrin assists in the strength and structure of skin and aids in epidermal hydration. Defective filaggrin expression has been widely demonstrated in people Key points • Initial management of atopic dermatitis (AD) involves education, assessment of triggers and exacerbating factors, and topical therapy. • Testing for food allergy may be considered if AD is severe or refractory, if skin flares follow specific exposures to foods or if there is a history of anaphylaxis. • Serology and skin prick methods of IgE testing have high rates of false-positive results. Careful interpretation of results is required, with confirmation of suspected food allergy by oral food challenge. • Inappropriate dietary restrictions can have severe nutritional consequences in children. Dietary restrictions should be reviewed regularly. • Testing for aeroallergen allergies is available. Interpretation of results and recommendations for management are, however, contentious areas. • Patch testing for delayedtype allergy is recommended if regional patterns of eczema suggest allergic contact dermatitis. MedicineToday 2014; 15(5): 42-46