There are clues that childhood diet may influence respiratory health and risk of asthma and allergies, but the evidence to date only comes from 'snap-shot' studies at one point in time. In order to get a clearer picture of whether diet in early childhood influences the development of respiratory and allergic disorders later in childhood we need large studies which have collected data from the same individuals more than once over time. ALSPAC has collected detailed information about the children’s diet at age 3, and about asthma and allergies when the children were age 7 and older. This dataset will allow us to discover whether children who developed asthma had a different diet when they were younger, compared to children who did not get asthma. In particular, we will investigate whether children who eat a ‘healthier’ diet (higher intake of fruit, vegetables and oily fish, rich in antioxidants and omega-3 fatty acids) are less likely to develop asthma and lower lung function, especially if they have a particular genetic make-up and are exposed to high levels of tobacco smoke and air pollution.