About 30 million Americans suffer from eczema, a painful, itchy skin condition that can be hard to treat and miserable to live with. Now the Food and Drug Administration has fast-tracked testing of a promising new drug treatment that could offer patients new hope.

Daniela Velasco is one of the patients taking part in testing the drug, called Dupilumab, at Mount Sinai Hospital in New York City, and she's amazed by the difference it has made. Velasco suffered from flare-ups so severe they kept her awake at night. Now she says her skin looks healthy for the first time in four years.

"It was such a quick change, so dramatic," she told CBS News. "Like from being extremely miserable to like, 'Whoa, this is what it feels like to be normal again!'"

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The itchy, red patches on her legs cleared up within 10 days. Doctors say 85 percent of the patients taking the drug in the study experienced similar results.

Dupilumab, which is administered by injection, was developed by Regeneron Pharmaceuticals, Inc. and Sanofi. It was recently designated a "Breakthrough Therapy" by the FDA to accelerate the testing process and speed its way towards approval.

The drug was developed based on research led by Dr. Emma Guttman-Yassky of the Icahn School of Medicine at Mount Sinai, which found that eczema is driven by the immune system. Dupilumab targets molecules that trigger the inflammation.

"We know that it's immune driven and we know that we have a large population that is in need of better treatment," Guttman-Yassky said.

The drug is currently undergoing Phase 3 clinical trials to prove its effectiveness, the last major hurdle before FDA approval.