Background
Cow's milk allergy (CMA) is the most common food allergy in infants and young children, affecting 2% to 3% of the general population. Most studies have shown the prognosis of developing tolerance to cow's milk to be good, with most outgrowing their allergy by age 3 years.
Objective
To define the natural course of CMA and identify the factors that best predict outcome in a large referral population of children with CMA.
Methods
Clinical history, test results, and final outcome were collected on 807 patients with IgE-mediated CMA. Patients were considered tolerant after they passed a challenge or experienced no reactions in the past 12 months and had a cow's milk IgE (cm-IgE) level <3 kU/L.
Results
Rates of resolution were 19% by age 4 years, 42% by age 8 years, 64% by age 12 years, and 79% by 16 years. Patients with persistent allergy had higher cm-IgE levels at all ages to age 16 years. The highest cm-IgE for each patient, defined as peak cm-IgE, was found to be highly predictive of outcome (P < .001). Coexisting asthma (P < .001) and allergic rhinitis (P < .001) were also significant predictors of outcome.
Conclusion
The prognosis for CMA in this population is worse than previously reported. However, some patients developed tolerance during adolescence, indicating that follow-up and re-evaluation of CMA patients is important in their care. cm-IgE level is highly predictive of outcome.
Clinical implications
The increasing potential for persistence of CMA, along with cm-IgE level's effect on prognosis, should be considered when counseling families regarding expected clinical course.
A more concise statement was provided by study author Dr. Robert Wood in a CNN story by Sharona Schwartz.
Researchers found a "significantly different natural history of milk allergy than what had been reported in virtually all of the previous studies. ... They would have said that the vast majority of milk allergy is outgrown by age 3 and if not by 3 certainly by 5 or 6," Wood said.
According to the study, which examined children who had been sent by a doctor to a pediatric allergy center, "the prognosis for developing tolerance [to milk] is worse than previously estimated."
The study found that 19 percent of the group outgrew their allergy to milk by the age of 4; 42 percent by the age of 8; 64 percent by the age of 12. The study found that 79 percent of the group outgrew their allergy to milk by the age of 16, which means one in five did not outgrow the milk allergy by that age.
The authors said that the character of cow's milk allergy "has changed over time ... and may now truly be a more persistent disease."
"One of the huge frustrations for parents of milk-allergic children is that they will typically find that someone with peanut allergy gets lots of respect and lots of precautions taken and the same respect is almost impossible to get for milk allergy," Wood says. Examples of precautions are cleaning school lunch tables well or placing children with peanut butter at a separate table. "Whatever precautions need to be in place for something like peanut allergy, need to be in place for milk allergy as well," says Wood.
The study also found that even though many did not outgrow the allergy by age 3, some patients were able to outgrow it "well into adolescence," indicating that "there is no age at which outgrowing CMA (cow's milk allergy) is impossible."
One very important caveat. The children in this group all have been referred to a pediatric clinic, and 91% had at least one other allergy besides that to dairy. Therefore, these children may be abnormally sensitive or prone to allergies.
And unfortunately, neither the article nor the abstract gives any indication of what parents can do, other than wait and hope that the allergy goes away. However, the study does give some diagnostic techniques may identify which children will have permanent allergies and which won't.
All in all, not very good news for parents of small children with dairy allergies.
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