As the holiday season approaches, blood banks nationwide are encouraging people to donate in an effort to combat a possible blood shortage.

“Generally during the holiday season, people are more preoccupied with shopping and decorations than giving blood,” said Karen Schwarz, senior marketing representative for Heartland Blood Centers, adding that blood shortages are very common during winter months.

There are 9.5 million blood donors in the U.S., but that’s not enough to meet demand if there was a sudden catastrophe this time of year, said Andrew Ross, a blood donor program recruiter for the University of Illinois Medical Center.

Ross said there would be a deficit of blood if thousands of people went to the hospital at once for transfusions. Even if healthy people donated immediately, it wouldn’t matter because blood is required by law to undergo processing for three to four days following donation to ensure it is safe to use, Ross said.

The recipients of blood donations are usually victims of car accidents or post-surgical patients, according to Lifesource.org, a Chicagoland blood center.

Ross said college-aged people are ideal candidates for donating blood because of their optimal health.

“Probably 75 percent of our donors are students,” he said. “[College students] are actually the healthiest. We know that younger people have fewer health problems.”

Eric Griggs, a freshman film & video major, has donated blood several times.

“I’ve donated blood all through high school at [blood] drives,” Griggs said. “[I wanted] just to help out. I had no opposition to it.”

To be eligible to give blood, donors must weigh more than 110 pounds, be older than 17 and not have any diseases that can be transferred through blood, according to Lifesource.org.

As more donors are sought, some people question why blood cannot be manufactured. Part of the issue is that blood is a complex substance consisting of multiple parts—platelets, plasma and red and white blood cells—that scientists have been unable to replicate synthetically, according to a 2009 article published in the Journal of the American Chemical Society.

Because scientists cannot manufacture an effective substitute for blood, doctors must rely on blood donations, which only stay fresh for 42 days, Ross said.

As the demand for blood increases during the holiday season, numerous drives will be held throughout Chicago to satisfy the need for greater quantities of blood.