Childrens’ allergies tend not to be isolated – a child with asthma may also have eczema, or asthma may precede hay fever. Clinicians call it the allergic march, or a tendency for one allergic condition to clear up only to be followed by another as the child gets older. Co-morbidity, which is the tendency for conditions to occur together, is also common.
Researchers at the Karolinska Institute in Stockholm, Sweden, now shed new light on allergy treatments and the allergic march, i.e. how children's allergies can develop over time. They looked at the BAMSE birth cohort which is a study looking at around 4,000 children born between 1994 and 1996 in various areas of Stockholm. The researchers obtained data on allergic march symptoms of eczema, asthma and rhinitis at the ages of 1,2,4,8 and 12 years. They also asked for information on parental allergy, breastfeeding and other relevant issues.
At the age of 12, around 1695 children who completed the study (58%) had had at least one allergy-related condition at some time. The presence of eczema peaked between the age of two and four years, while rhinitis increased in prevalence with increasing age. Between the ages of 4 and 12, the prevalence of asthma remained stable.
Among children with parental allergy, there were 66% who had an allergy themselves, compared with 52% of those whose parents did not have an allergy. Co-morbidity became more common with age. At 1 year, just 1.8% of children had at least two allergy-related diseases, but at the ages of 2,4,8 and 12 years, the figures were 2.3%, 5.9%, 5.5% and 7.5%. Co-morbidity was more common when the parent had an allergy.
Asthma did not occur on its own as often as eczema or rhinitis. At 1 year, asthma was associated with eczema and/or rhinitis in 38%, and in 67% at 12 years. Only 42% with eczema and 33% with rhinitis had other allergies at the age of 12. Overall, the researchers noted that there was a lot of disease ‘turnover’ with many new and remitting cases occurring.
In conclusion, allergy affected the majority of children during their first 12 years. The development of eczema, asthma and rhinitis is indeed a dynamic process (the ‘allergic march’). The strength of this study is that it is prospective – following the children as they develop. So it does not depend upon recall, which may be faulty. Further research ought to focus on the different disease types – also known as phenotypes – which may define the individual child’s progression through the allergic march.