A hazmat crew and at least five ambulances were sent to Wild Wings Cafe, 7900 Brier Creek Parkway, in the Brier Creek Commons shopping center around 8:30 p.m.
A worker pouring Drano and Clorox down the drain was overcome by the odor and was taken to the hospital, officials said. A patron sitting near the drain was also being treated at the hospital.
Both had non-life-threatening injuries, officials said.
Several other customers complained of burning eyes but did not require hospital treatment.
The restaurant closed following the incident on Friday night but reopened as scheduled on Saturday.