The Army and Air Force Exchange Service is pulling all products containing aspirin from the shelves at its contingency locations.

Department of Defense officials ordered that aspirin in combat zones be controlled and now prohibit over-the-counter access through AAFES and Morale, Welfare and Recreation activities, an AAFES press release stated.

In an order written in March by then-Assistant Secretary of Defense for Health Affairs Ward Casscells, service officials were told to make sure all U.S. troops and civilians headed into combat zones stop taking aspirin at least 10 days before they deploy, unless directed by a health care provider.

The goal of the policy is to minimize blood loss in combat injuries, he wrote, and cut down on the number of "preventable deaths" associated with those wounds.

The concern over aspirin stems from how it affects blood’s ability to clot.

"Basically, what it does is it inhibits platelet activation and aggregation," said Air Force Col. David Schall, the command surgeon at the U.S. European Command’s headquarters. "This effect lasts for five to seven days after you take aspirin.

"If your platelets aren’t working, you are going to continue to ooze and ooze."

Aspirin blocks an enzyme in platelets, he added.

Someone who took aspirin and is injured will have a higher rate of blood loss, and the larger the surface area of the injury that is bleeding, the bigger the problem, Schall said.

An acceptable alternative to aspirin is Tylenol, which is recommended instead of aspirin at those contingency locations, Schall said.

"Advil can have an effect on the platelets as well, but aspirin seems to be more potent," Schall said.

Schall said he has not seen any similar orders that stopped aspirin from being sold over the counter at exchanges or commissaries before, but people with the flu have been prohibited from taking aspirin because such usage can cause a potentially fatal syndrome called Reyes syndrome, which affects the liver and brain.

AAFES officials said they received the order April 9 and started pulling the products April 14. They have been told to keep alternatives including Advil, Datril, Motrin, Tylenol and Aleve on hand at their locations in and near combat zones.

The order resulted in AAFES removing more than 248,000 bottles from 95 facilities that serve troops in Operation Iraqi Freedom and Operation Enduring Freedom combined, Army Lt. Col. David Konop, an AAFES spokesman, wrote in an e-mail.

Commands have been asked to educate their servicemembers about the new policy before they deploy and AAFES has posted signs regarding the change at all of the affected facilities, Konop wrote.