The Red Cross put out a emergency request for blood donors this month, hoping to make up for last month, when it got 50,000 fewer units than projected.

But that request did not go out to everyone: For the last 30 years, any man who has ever had sexual relations with another man is permanently disqualified from donating blood.

This policy, based on fear from the early days of the AIDS epidemic, has not kept up with advances in testing procedures or a full understanding about dangerous sexual practices.

It is right to make the blood supply as safe as humanly possible, but it is wrong to stigmatize one group of people who want to help and could do so without putting recipients at risk.

The ban on gay donors started in 1983, when there was a legitimate concern about who might pose a threat to the blood supply. Outbreaks of AIDS were most common in the gay community and among intravenous drug users, but there were also infections among hemophiliacs, who received regular doses of clotting factor derived from donated blood.

At that time, HIV, the virus that causes AIDS, had not been identified, and testing blood donations was not practical. But since then, both things have changed.

Now every pint of blood donated in the United States is tested before it is used. We can be more specific about who can contribute and who cannot.

Even though many of the AIDS cases in the United States are among gay men, it’s not a gay disease. In Africa, where AIDS is spreading in epidemic proportions, it is a heterosexual disease. As discoveries were made about AIDS and how it spreads, there has been significant public health education about safe sex practices. There are gay men who don’t practice safe sex, but the same is true for heterosexuals.

Blood donors can have just received a tattoo or piercing and still give blood. They can have been treated for syphilis, gonorrhea, chlamydia, venereal warts or genital herpes. Blood donors can have had sex with a prostitute, as long as it wasn’t in the last year.

But sex between two men is treated as something more dangerous than any of these other factors. It doesn’t make sense.

Creating a more nuanced policy that identifies who should and who should not give blood is not a matter of civil rights for gay men (although this exclusion is based more on prejudice than on science). It is about securing an adequate and safe blood supply for people who need it.

Blood banks and public health authorities should continue their work to create a new policy that reflects what we have learned in the last 30 years.