New studies show that allergies to milk and egg are harder to outgrow than has been widely accepted.
Researchers from Johns Hopkins Children's Center in Baltimore in the United States have found that while food allergies such as those to milk and egg were usually outgrown by age three a generation ago, that is no longer the case with the allergies now often persisting for much longer.
Milk allergies affect 2 per cent of children and eggs allergies 3 per cent in the US. This makes them the two most common food allergies in the country. The latest findings come from two seperate studies which are both published in the Journal of Clinical Immunology.
Lead researcher Robert Wood, M.D., head of allergy and immunology said: "The bad news is that the prognosis for a child with a milk or egg allergy appears to be worse than it was 20 years ago."
"Not only do more kids have allergies, but fewer of them outgrow their allergies, and those who do, do so later than before."
Dr. Wood and his team looked at the medical records of more than 800 children with milk allergies and nearly 900 with egg allergies going back 13 years. What the researchers found was in marked contrast to the currently accepted figures based on previous research.
While 75 per cent of children with milk allergy have previously been reported to outgrow their condition by age 3, the new study indicated that only 20 per cent of children may outgrow their allergy by the time they are four. The figures go on to show that only 43 per cent were free of milk allergy by age 8.
A similar trend was evident in the cae of egg allergy with only 4 per cent outgrowing it by age 4, and 37 per cent by age 10.
Dr. Wood and colleagues did discover however that many of the children studied did eventually outgrow their allergies to milk and eggs. Their data showed that 79 per cent of children withmilk allergy and 68 per cent with egg allergy were able to tolerate these foods by age 16.
The results also suggested that some of the children were able to overcome their allergies when older than 16 suggesting that it is important to carry on testing into early adulthood.
Finally, Dr. Wood and his team noted a correlation between a child's blood levels of milk and egg antibodies (IgE) and the time that the allergies persisted. The higher the level of antibodies, the longer the time to outgrow the allergy.
"Our data suggest that this does not happen as early as previously thought. Furthermore, we have identified an egg IgE level of at least 50 kU/L as a marker of persistent egg allergy," the researchers wrote in the Journal of Clinical Immunology.
Wth respect to milk allergies they said: "Our findings stand in marked contrast to the study that is most often quoted, which found that 75 per cent of children with IgE-mediated milk allergy were tolerant by the age of three years. One positive finding is that patients did continue to achieve tolerance well into adolescence."
The researchers concede that their findings may have been skewed by the fact that they tend to see children with more severe allergies. However, they conclude that food allergies today are more aggressive than they have been in the past. Why this may be they are currently unsure.
Sources: J.M. Skripak, E.C. Matsui, K. Mudd and R.A. Wood The natural history of IgE-mediated cow's milk allergy Journal of Allergy and Clinical Immunology Nov 2007 120(5): 1172-1177
J.M. Skripak, E.C. Matsui, K. Mudd and R.A. Wood The natural history of egg allergy Journal of Allergy and Clinical Immunology Dec 2007 120(6): 1413-1417