WASHINGTON — The Food and Drug Administration has reopened the comment period for its 2007 proposed rule on labeling foods as “gluten-free.” One of the criteria proposed is that foods with a gluten-free claim may not contain 20 parts per million (p.p.m.) or more of gluten, which is similar to gluten-free labeling standards used by other countries. The validated methods in 2007 were not able to detect the amount of gluten in a food reliably when the level was less than 20 p.p.m. The proposed rule conforms to the standard set by the Codex Alimentarius Commission in 2008.

“Before finalizing our gluten-free definition, we want up-to-date input from affected consumers, the food industry and others to help assure that the label strikes the right balance,” said Michael Taylor, the F.D.A.’s deputy commissioner for foods. “We must take into account the need to protect individuals with celiac disease from adverse health consequences while ensuring that food manufacturers can meet the needs of consumers by producing a wide variety of gluten-free foods.”

People who have celiac disease are unable to tolerate gluten, which is a protein found in such grains as wheat, rye and barley.

The gluten-free comment period will open at noon Eastern Daylight Time on Aug. 3 and remain open for 60 days. People interested in commenting should go to docket number FDA-2005-N-0404 at www.regulations.gov. To submit comments by mail, send them to The Division of Dockets Management, HFA-305, Food and Drug Administration, 5630 Fishers Lane, Room 1061, Rockville MD 20852.