February 2, 2011

Peanut Allergies Lesss Common: Study

A new study on allergy diagnoses in England, published in the Journal of Allergy and Clinical Immunology, concludes that peanut allergies are less common than previously believed.

Reuters reports the study also found that while the proportion of the population that is affected by peanut allergies is relatively small, it has grown over time.

Both parents and researchers have become more concerned about peanut allergies in recent years. Studies in the past have shown that in some regions around the world, as many as 2 in 100 children could have peanut allergies. However, the current study found that that number is more like 2 in a thousand children.

The differences between the conclusions in the new study and previous ones may be in the way rates of allergy were calculated.

"Overall, the 'true' prevalence of peanut allergy is likely to lie somewhere between these various estimates," Dr. Aziz Sheikh, one of the paper's authors from the University of Edinburgh in Scotland, told Reuters Health by email.

Sheikh and colleagues analyzed data taken from a database of all diagnoses by general practitioners in England between 2001 and 2005. The database included more than 400 practices treating nearly 3 million patients.

The study found, on average, among kids under 15 years of age, only about 2 in every thousand had received a diagnosis of peanut allergy at some point. The team found the highest rates came from boys between ages 5 and 9.

Taking the entire study population into consideration, which included adults, they found that about two out of every 4,000 people had a peanut allergy in 2005 -- double the 2001 finding of one in every 4,000 people.

According to their findings, Sheikh and his colleagues said there was about 26,000 cases of diagnosed peanut allergies among all practices across the study.

They wrote in the journal that it is possible that the figures underestimate the true prevalence of peanut allergies because some allergies are never recorded by practitioners.

Dr. Ruchi Gupta, a pediatrician at Northwestern University's Feinberg School of Medicine in Chicago, agrees with the team's assessment.

"Allergies are something that, although the generalist physicians should know about it, often times patients go straight to a specialist," Gupta told Reuters Health.

The researchers still believe that the study was more accurate than some previous studies, which relied mainly on people reporting their own allergies or their children's allergies. In those studies, people tend to not only report allergies, but also less severe reactions that do not qualify as allergies.

Dr. Scott Sicherer, of the Mount Sinai School of Medicine, published an article in the same journal noting the difficulty in estimating the prevalence of food allergies in a population. The difficulty arises both because some tests do not diagnose true allergies, and because allergies may show up or go away at certain times in life and some people living in different areas may be exposed to certain allergy-triggering foods but not others, he wrote.

While the current study and previous ones do not agree on the actual prevalence of peanut allergies, there is a general agreement among researchers that the rate of recorded allergies is increasing.

Sheikh said the trend may be due to better diagnosis of peanut allergies and better recording by doctors.

Gupta, however, said that the increasing prevalence could reflect an upswing in actual allergies, and not just the fact that peanut allergies are more likely to be recognized now than in the past. However, she acknowledged that the reasons are unclear.

"There's a ton of theories "¦ from the hygiene hypothesis to how we process our foods in today's world," she said.

It is also unclear whether peanut allergy rates are increasing only in industrialized nations or if they are increasing everywhere but only being recorded in some countries like the US, Canada and Europe, said Gupta.


On the Net: