I have purpura, is there a vitamin that would help control this?

No. Senile purpura is a common condition that affects middle-aged and elderly, fair skinned persons. Typically, the forearms and anterior legs are affected. Areas that are not exposed to the sun are unaffected. It is caused by chronic sun exposure, which results in permanent thinning of the skin and not a vitamin deficiency. It is likely that this is what you have.