in 1999 demonstrated no positive effect from the application of topical vitamin E. Scarring of veins may also cause problems for further attempts to draw blood, such as for medical procedures. This may confuse phlebotomists who may believe they have missed the vein due to the higher pressure needed to penetrate the scar tissue. See also Blood transfusion Blood donation References Further reading Circular of Information for Blood Products, page 32 (page 35 of the PDF) External links American Society for Apheresis Transfusion medicine Blood donation