In recent decades asthma and allergies had great increase worldwide, being currently a serious global health problem. The causes of these disorders are unknown, but the most accepted hypothesis is that improving hygiene and reducing infections may be the main cause of this increase. Both asthma and allergies are complex diseases with strong environmental influence, so the use of versatile tools such as genetic programming can be important in the understanding of those conditions. We applied genetic programming to data obtained from 1296 children. Data related to chronic viral infections and environmental factors were used to classify in asthmatic and non-asthmatic, IgE and SPT in order to assess allergy. For asthma, viral infections were not relevant while for IgE and SPT they were. The use of genetic programming is shown to be a powerful tool to help understand those conditions.