Chapter 14 Managing the Allergic Child
Introduction
Children with allergies present a special challenge to the physician. First, they are frequently affected at more than one body site and may, in countries like the UK where allergists are scarce, be under the care of several different specialists. Second, the condition can progress. There is a well-described atopic march in which children born with atopic dermatitis can go on to develop asthma and then rhinitis/conjunctivitis. Children who are monosensitized to peanut tend to develop allergy to additional tree nuts over time.
A switch also occurs in the allergens recognized, with many children being initially food allergic (milk, egg, wheat, soya), losing these allergies only to develop inhalant allergies at around the age of 4–6 years. Thus there is a need to treat not only the existing condition, but also to attempt to prevent further disease progression.
Allergy and infection frequently coexist in children – recognition and appropriate treatment of both is important.
Epidemiology/Prevalence/Burden
Allergic diseases exist worldwide and are highest in westernized countries. In the UK, which leads the world for asthma symptoms, the burden in 13–14 year olds as judged by the International Study of Asthma and Allergy in Childhood (ISAAC) study, shows 32% reporting symptoms of asthma, 9% eczema and 40% allergic rhinitis. In the UK some 12 million people are affected by allergic disease in any one year. One in 70 children is peanut allergic and this figure is rising. Highly atopic children can be severely disabled by their disease with gastrointestinal symptoms including gastroesophageal reflux disorder (GERD), failure to thrive, severe atopic dermatitis, and life-threatening anaphylaxis. Even those children with less problematic disease such as seasonal allergic rhinitis can be disadvantaged because of poor sleep, decreased concentration, and a reduction in examination performance.
Classification of the Problem
Children are usually classified by the allergic disorders from which they suffer. These are likely to include one or more of atopic dermatitis, atopic gastrointestinal disease (gastroesophageal reflux, food allergy, failure to thrive, eosinophilic esophagitis, etc.), atopic respiratory disease (asthma, rhinoconjunctivitis), anaphylaxis, urticaria (rarely allergic in childhood), and drug allergy. Children very rarely exhibit allergy to occupational allergens such as latex, nor to aspirin. An alternative classification is by allergen sensitivity – food allergy, inhalant allergy, or both.
Secondary conditions, often infective, are frequent. For example, the child with rhinitis may develop rhinosinusitis or otitis media with effusion, or suffer a viral URI which exacerbates existing asthma.
At the Royal National Throat, Nose and Ear Hospital we have a multidisciplinary approach with allergist, pediatrician, ENT surgeon, audiologist, and dietician present in the same clinic together with an allergy nurse. In this way the many problems of an individual child can be addressed in one visit without excessive time off school.
Relevant Anatomy and Physiology
Children are not simply small adults, and therefore allergic disorders present differently. For example, the short relatively horizontal Eustachian tube means that nasal disease frequently impinges on the middle ear in children. The mild immunoincompetence seen in most children under 2–3 years (due to the time of maturation of the IgG2 response and delayed maturation of IgA) means that allergic respiratory disease is often accompanied by infection, which may mask the underlying allergy.
The physiology of children can also differ from that of the adult. Children are relatively tolerant of severe allergic reactions (anaphylaxis) and of epinephrine (adrenaline) treatment, probably because of their atheroma-free cardiovascular systems. Drug metabolism can differ: small children may exhibit paradoxical excitement with antihistamines. Many drug therapies available for adult disease have not been adequately tested in childhood, especially in children under 5 years.
Pathophysiology
The pathophysiology of the allergic response is similar in children to adults. It is now thought that a T-helper (Th) 2 bias exists during pregnancy to prevent fetal rejection. The baby is born with a Th2 biased immune system, but this gradually switches over the following months to one with a preponderance of Th1 responses. In atopic individuals the Th2 responses do not wane, but persist – initially largely directed against food allergens; later inhalant allergens form the major response provokers.
Diagnosis
History
Taking an adequate allergy history is vital, especially in children. This should involve not only the presenting complaint, its duration, timing, provoking factors, relieving factors, etc., as in adults, but should also involve a history of pregnancy, birth, postnasal issues, and development including early feeding and the presence or absence of colic, failure to thrive, etc. It is necessary to ask about possible allergic symptoms at other sites.
A family history of atopic disease should be noted as well as a very detailed environmental history, feeding, pets, nursery placement, smoking in the home, etc. Many children lead complicated lives and live in a least two places – symptoms occurring at one only can give a clue to causation, for example the child who coughs when visiting his father who has a cat. Any treatments given, including alternative and complementary ones, need to be accurately recorded, plus the response to these.
A history (questionnaire) is often helpful as it can be filled whilst waiting to be seen and focuses the attention of parents.
Physical Examination
Many children are initially shy, so it is worthwhile spending time getting to know them and amusing and involving them in the consultation prior to making any attempt at examination. Much information can be gained by quiet observation whilst taking the history: an allergic salute may be seen, a double allergic crease under the eyes may be noticed, dry eczematous skin can be apparent. The quiet withdrawn child may not be able to hear properly.
Prior to the consultation the child should have the weight and height recorded by the clinic nurse, and it is sensible to repeat these at each visit, especially if the child is receiving either nasal, inhaled, and/or topical corticosteroids.
The skin should be examined for signs of atopic dermatitis particularly on the face and in the elbow and knee flexures. Examination should involve looking at ears, nose, and throat. An otoscope is useful for all three, but may need to be supplemented by nasal endoscopy in older children if rhinosinusitis is suspected. Chest examination should include observation of chest shape: an indrawn lower chest suggests an upper airway obstruction. Wheezing may be audible. The abdomen should be examined if there is any gastrointestinal complaint.
Investigations
Skin Prick Tests
These can be undertaken in children from a few months of age. In small children it is sensible to have them cuddled up to their parent or caretaker and the back can be used for a few skin tests as directed by the history. Older children may tolerate testing on the forearm. We employ a play leader to distract the child – often by getting them to blow bubbles – during the process.
Skin prick tests in children tend to be regarded as positive when they are 2 mm larger than the negative control rather than the 3 mm cut-off point commonly used in adults. As in adults correlation with the history is vital. As with adults, if there has been previous anaphylaxis then skin prick testing should be undertaken with care and the allergen may need to be tested in dilutional titers.
Laboratory Tests
If skin prick testing cannot be undertaken due to severe atopic dermatitis, recent drug therapy such as antihistamines (children’s cough medicines often contain antihistamine and can be confounding factors), anaphylaxis, dermatographism, then blood can be taken for antigen-specific IgE tests as an alternative.
Other blood tests which may be useful are:
Nitric Oxide
Exhaled nitric oxide is usually low (<20 ppb), but is raised when there is lower respiratory tract inflammation from any cause. The test is usually possible in children over 5 years and can be a useful pointer to underlying asthma. Conversely normal levels in the coughing child suggest that the problem is located in the upper respiratory tract.
Nasal Nitric Oxide
This is useful when very low as this should raise the suspicion of primary ciliary dyskinesia as an alternative diagnosis to chronic allergic rhinitis. Specialized tests of ciliary beat frequency and electromicroscopy are then indicated.
High levels suggest inflammation which could be allergic. Mid range values do not necessarily imply normality.
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