WASHINGTON — Secondary airport screenings for passengers with headwear have left some Sikhs, whose religion requires men to wear turbans, feeling racially profiled and embarrassed.

While other airline passengers are protesting the federal Transportation Security Administration’s full-body scans and rigorous pat-downs because of privacy concerns, Sikhs, with a population in the U.S. of about 500,000, are also protesting on religious and racial grounds.

Turban wearers are often subjected to secondary screenings, even after passing through advanced imaging machines made to see through clothing. Turbans, according to the TSA, or any “bulky” clothing are registered as an “anomaly” requiring increased scrutiny, which Sikh groups see as racial profiling.

The policy for secondary screening of “bulky” clothing has been in place since 2007, but the TSA has acknowledged that it needs to do a better job informing the public about procedures.

TSA Administrator John Pistole, in a recent congressional hearing, called the advanced imaging machines “the best available technology today” that will help detect non-metal threats.

Sikh groups had hoped the imaging machines would create equality in screening measures and help avoid situations like the one a Maryland man recently experienced when passing through Chicago O’Hare International Airport.

Gurdeep Singh Bawa, a Sikh from Potomac, Md., had no problem at Baltimore-Washington International Thurgood Marshall Airport in September, but on his return home through Chicago he had to remove his turban after clearing a metal detector.

“I’ve never been humiliated like this in my life,” Bawa said. Bawa and his 24-year-old son, also wearing a turban, passed through the detector, but then were told they must go through an explosives trace detection test, he said.

“You’re sitting there and there are all these people going by and they think we’re criminals,” he said.

TSA officers put a residue-detection chemical on his hands and let him pat down his own turban, since he doesn’t let anyone touch it for religious reasons, he said.

His son passed this test, but the officers told Bawa he had set off an alarm and called the police, who checked his records in Maryland, he said. He was tested again and came away clear, but was told that since he set off the alarm once, he would have to take his turban off, he said.

“Taking it off is very disrespectful for us,” Bawa said.

Responding to a request for comment about the incident, the TSA said in an e-mail that it recommends removing all headwear, “but the rules accommodate those with religious, medical, or other reasons for which the passenger wishes not to remove the item.” Although Bawa had religious reasons for keeping his turban on, he went into a private room and reluctantly took it off. Officers took his turban away and brought it back minutes later.

According to TSA policy, “officers must use their professional discretion to determine if a particular item of clothing could hide a threat object.” But Bawa called the TSA officers’ actions “excessive.” ”I think security is important, but this is too much,” Bawa said.

Sikhs are being “religiously, racially profiled,” said Hansdeep Singh, staff attorney for United Sikhs, a U.N. affiliate.

Seeing Sikhs go through extra screening because of their turbans will only reinforce some other passengers’ stereotypes, Singh said. The perpetuation of negative stereotypes is one reason Sikhs are still facing “hate crimes and bullying,” he said.

“The ramifications of this go far beyond secondary screenings,” Singh said.