Lesson of the week: Horse allergy in children

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Abstract
Case reports Case 1—Within minutes of riding a pony at a fête, an eight year old boy developed angio-oedema and respiratory distress. On initial assessment in the accident and emergency department, he was tachypnoeic with a saturation of 90% in air. He improved after treatment with oxygen, nebulised salbutamol, intravenous hydrocortisone, and intravenous chlorpheniramine. Skin prick testing produced a 6 mm weal to horse dander and a 3 mm weal to house dust mite (positive histamine control, 3 mm). He was advised to avoid horses, to carry chlorpheniramine in case of accidental exposure, and to use inhaled salbutamol and intramuscular adrenaline in the event of respiratory symptoms. Case 2—A nine year old boy was referred because of poorly controlled asthma despite receiving inhaled beclomethasone 400 μg/day. His asthma diary showed dips of more than 50% in his peak expiratory flow on Friday evenings (figure). These dips persisted all weekend and were associated with a persistent cough. One concern was that psychosocial circumstances at home might have accounted for his deterioration at weekends, but this was unfounded. His parents mentioned that he had once had a weekend free of symptoms when his sister had been away (figure). On Friday evenings his sister went riding, and she kept her riding gear in their bedroom. Further questioning showed that on direct exposure to horses he experienced rhinitis, conjunctivitis, and wheeze. Skin prick testing with horse dander produced an 8 mm weal (positive histamine control, 3 mm). His asthma was controlled once his sister stopped riding. He no longer requires inhaled steroids. Case 3—A five year old boy was referred with asthma. For two successive summers he had required treatment in the accident and emergency department for wheeze and sneezing, which developed while walking through fields. On the first occasion he had been eating an ice cream with nuts. The episodes were thought to be due to either nut allergy or hay fever. Skin prick testing, however, produced no reaction to nuts and a small weal (2 mm) to grass pollen (positive control, 4 mm). Closer questioning showed that on both occasions he had come into close contact with a horse. Skin prick testing to horse dander produced a 12 mm weal. He was advised to avoid horses and prescribed chlorpheniramine and a salbutamol inhaler for use if accidentally exposed.