Blood donation is essential; hospitals rely on donors to maintain a healthy blood supply to help patients. Both whole blood and portions of the blood, like the platelets only, are needed for therapeutic use. While there are a few things that can preclude a person from giving blood, such as recent travel to an area affected by malaria, or not having enough iron in the blood, there are medications that are not good for blood donors as well.
Aspirin is one medication that prevents a person from being a donor of platelets. That's because platelets, or thrombocytes, are impacted by aspirin. Typically, a protein called thromboxane springs into action after a wound, working to clot blood by constricting blood vessels and getting platelets to clump up. But aspirin inhibits the activity of thromboxane. That means blood can flow more freely after aspirin exposure, and that is bad news for patients in hospitals, some of whom desperately need platelets that can clot.
It only takes a few days for the platelets of blood donors to return to normal, and donations can resume about 48 hours after the ingestion of aspirin.