A new study suggests that peanut allergies in kids have increased threefold in the United States from 1997 to 2008, a startling drift, which cannot be clarified as yet.

Study Author, Scott H. Sicherer, MD, of the Jaffe Food Institute at Mount Sinai School of Medicine, tells WebMD, "We don't know why this is happening, but there are many theories".

Sicherer says that peanut allergy, different from other food allergies, is rarely outgrown and is one of the most hazardous food allergies.

His research group reviewed 5,300 families in 2008 and found that 1.4% of youngsters were believed to suffer from peanut allergies, over three times the 0.4% rate found when a comparable score was taken in 1997.

The study says that the percentage of kids with allergies to peanuts or tree nuts surged to 2.1% in 2008 from 0.6% in 1997, while lingering at 1.3% for grown-ups.

Sicherer tells WebMD that one theory for the increase, the hygiene hypothesis, says that "we've become very good at preventing natural infections, and the immune system is not chewing on things it would normally be chewing on".

The theory implies that "clean living" and more drug usage has left the immune systems in a state, which is more inclined to attack undamaging proteins, like those in foods, pollens, and animal dander.