A study published in this month's American Journal of Respiratory and Critical Care Medicine, a journal of the American Thoracic Society, found that children who start nursery before the age of two are twice as likely to experience wheezing in the first year of life.
Children who went to nursery at an early age and had older siblings were more than four times as likely to experience infections and symptoms associated with allergies.
Previous research has suggested that children who attend nursery and have older siblings build a greater immunity to asthma and allergies through increased exposure to germs.
However, the new study by Dutch researchers found that children who had increased exposure to germs experienced more airway symptoms, and children without older siblings and who did not attend nursery had fewer symptoms until the age of eight.
The researchers followed nearly 4,000 children over eight years. Parents completed questionnaires during pregnancy, when children were three months and 12 months old, and then yearly, reporting their child's airway symptoms.
Children were categorised as either early attendees, starting nursery before two years of age; late attendees, starting nursery between two and four years of age; or non-attendees.
Dr Johan de Jongste, who led the study, said, 'Early daycare should not be promoted just for reasons of preventing asthma and allergy.
'Early daycare merely seems to shift the burden of respiratory morbidity to an earlier age, where it is more troublesome than at a later age.'
Dr Elaine Vickers, Asthma UK's research relations manager, said, 'The best advice we can currently give to parents is not to smoke around their children and make sure they have a balanced diet and get plenty of exercise.'
