As news spread of Sunday’s mass shooting at a gay nightclub in Orlando, Florida, volunteers in Baton Rouge and across the country began streaming into blood banks with sleeves rolled up and arms out.

A rush of blood donations following tragedies is common, blood center officials say, as people search for a way to offer their help. A memorial on the Baton Rouge riverfront Monday evening included calls to give blood and fliers for blood drives Tuesday.

But for many in the LGBT community in Baton Rouge and elsewhere, the surge of blood donations has also highlighted a bitter irony: Federal regulations continue to ban gay or bisexual men from donating if they’ve had sex anytime within the past year. The policy apparently is designed to guard against HIV, but it’s been criticized by some as discriminatory.

“It feels like somebody slammed a door on you when you’re trying to do one of the only things you can do to help the people injured in this shooting,” said Matt Patterson, managing director of Equality Louisiana, an LGBT advocacy group.

The rules, first implemented in the 1980s at the height of the AIDS crisis, originally prohibited any man who has had sex with another man at any point in their lives from giving blood in the U.S.

Under loosened guidelines, issued by the Food and Drug Administration in December after years of criticism from advocacy groups, blood centers can now accept donations from gay and bisexual men who haven’t had sex in at least 12 months.

The yearlong abstinence requirement addresses concerns about a “window” between HIV exposure and when evidence of HIV shows up on blood screening tests. Federal regulators also have pointed to significantly higher rates of HIV among men who have sex with other men.

But critics of the waiting period have pointed out that advances in screening technology have made that window much smaller. Current tests can detect HIV in a person’s donated blood within two weeks of the first exposure.

“It’s ignorance of science and blood being tested,” said Ranji Bercegeay, a Baton Rouge nurse who works with the area HIV advocacy group HAART. “It’s just discrimination. We need to call it what it is.”

On Sunday evening, the Rev. Keith Mozingo, pastor of the Metropolitan Community Church of Baton Rouge, which was founded to cater to LGBT people, said he was touched to see images of the thousands of people turning out to donate blood in the aftermath of the attack, saying the outpouring of support is an indication of how far the LGBT community has come toward greater acceptance.

But a few moments later, Mozingo added that the blood donation policy also is a sign of the continued discrimination.

“I haven’t been able to give blood in years even though I’m HIV-negative,” Mozingo said. “The irony of us having a blood drive but not able to give blood — there’s still that stigma attached.”

At LifeShares Blood Centers in Baton Rouge on Tuesday, Wendell Jones, the company’s executive director for technical operations, said they’d seen a spike in the number of people donating since the Orlando attack — but added that Tuesday also was World Blood Donor Day, which the group also promoted.

“I understand it’s difficult for those who are wanting to give and would like to give,” said Jones, who added that BloodShares is reviewing the new guidelines issued in December and considering whether to allow donations after the 12-month window, something that requires blood centers to clear several regulatory steps.

“The policies from the government, which we’re bound to follow, are conservative,” Jones said. “But it’s conservative because of safety.”

The FDA has defended the policy, saying it’s based on sound science. Data from the Centers for Disease Control and Prevention show that men who have sex with other men are at significantly greater risk of HIV exposure than other members of the population.

But Patterson, the LGBT advocate, said subjecting gay and bisexual men to a blanket one-year waiting period before giving blood singles them out in a way other people at higher risk of HIV infection — including sexually promiscuous heterosexual people — aren’t.

“It still feels as if accurate science and medical knowledge is not what’s driving that policy,” Patterson said. “People are still not willing to let go of a kind of visceral disgust.”

Follow Bryn Stole on Twitter, @BrynStole.