By Stephanie Stahl

PHILADELPHIA (CBS) — The Children’s Hospital of Philadelphia has helped cure a teenage boy of his egg allergy.

Making chocolate chip cookies with eggs used to be something that was life-threatening for 15-year-old Isaac Keiser.

“I have anaphylaxis, so my throat will close up and I get hives and vomit and I am always in constant fear that’s going to happen,” said Isaac.

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His childhood was spent avoiding exposure, which is no easy task considering eggs are in so many things.

“He couldn’t go to the restaurant and order a hamburger because earlier that morning they cooked an egg on that same grill. It’s terrifying,” said Isaac’s mother, Gwen Keiser.

Keiser made sure her son was always equipped with an epi pen, but he still had to be careful about an accidental exposure.

“I always had to get out when everybody had cake or something,” said Isaac. “Just makes you kind of different and separate from everybody else.”

That’s all changed now because Isaac was the first patient to be desensitized to eggs at Children’s Hospital of Philadelphia.

Dr. Jonathan Spergel, chief of the allergy section at CHOP, says allergies to things like milk, eggs or peanuts are caused by an overreaction of the immune system.

“In school, it’s about one kid per classroom, so this is a huge thing,” said Spergel.

Desensitization starts with tiny exposures to the allergen that’s causing the reaction.

“You slowly get your body used to it,” said Spergel.

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It took a while, but Isaac can now enjoy cookies and eat anything with eggs.

“It’s all very new because I’ve been very sheltered from all these foods and now I can try them all,” said Isaac. “It’s all very overwhelming but so exciting.”

“I cannot tell you how fantastic it is,” said Keiser. “It literally has been life-changing.”

Now, instead of fearing chocolate chip cookies, Isaac can devour them.

The research on treating allergies is continuing at CHOP and the doctors there say it has to be done with medical supervision.

It’s not safe to expose children outside a hospital setting.

Stephanie Stahl