hours prior to donation. (Guidelines vary by blood center.) The reason is that aspirin can prevent platelets from adhering to clot bleeding. Some blood centers also prohibit the taking of any non-steroidal anti-inflammatory drug (NSAID) for 36 hours prior. Secondly, one is generally allowed to donate platelets anywhere from every 3 to 28 days. This is a stark contrast to whole-blood donation, which has an eight-week (or longer) waiting period between donations. Along those lines, since platelet donation does temporarily remove whole blood from the body, it may be necessary to wait eight weeks after a whole blood donation to donate platelets, although two weeks is more common. In the US, a donor is only allowed to donate 24 times each year and may not lose more red blood cells or plasma in a year than they would from the maximum allowable number of whole blood donations. In India, as per Ministry of Health the blood donation interval criteria for apheresis requires at least 48 hours interval after platelet/plasma - apheresis. The donation should not be done more than two times a week and should also be limited to 24 times in one year. Thirdly, additional tests may be required before becoming a donor for the first time. These tests may establish a platelet count. Newer automated platelet pheresis machines do that as the donation begins, and adjust accordingly the quantity of platelets to be drawn. Tests may also determine the donor's compatibility with particular recipients through a human leukocyte antigen (HLA) test. Multiparous women may be excluded from becoming donors due to heightened TRALI risk. These tests usually involve nothing more involved than the drawing of several tubes of blood. Adverse events Adverse conditions that can happen during a plateletpheresis donation are hypocalcemia, hematoma formation, and vasovagal reactions. The risk of these conditions happening can be reduced or prevented by pre-donation education of the donors and change of apheresis machine configuration. Vein scarring Repeated platelet donations at short intervals will cause the venipuncture site to scar. While cosmetically it is virtually invisible, the scarring also occurs on the vein itself, making it harder to insert a needle on future occasions. Anecdotal reports have said that rubbing vitamin E oil (or the insides of a vitamin E capsule) on the venipuncture site may reduce scarring. However, a study conducted by the University of Miami Department of Dermatology and Cutaneous Surgery