Table 1. Diagnostic codes for electronic health records.

Outcome	Definition. Any record of the following in the e-HR
Wheeze	Wheeze or asthma excluding wheeze in the context of bronchiolitis
Cough	Cough excluding cough in the context of URTI or LRTI
URTI	URTI, pharyngitis, rhinorrhoea, laryngitis, tonsillitis, sinusitis or otitis media. Or at least two of fever, sore throat, earache, sticky eye or cough
LRTI	LRTI, chest infection, respiratory infection, bronchitis or pneumonia. Or cough with a record of signs of infection such as crackles on auscultation
Bronchiolitis	Bronchiolitis
Food allergy	Doctor diagnosed food allergy
Eczema	Eczema or eczematous skin

URTI (Upper respiratory tract infection), LRTI (Lower respiratory tract infection).