 The investigators propose that nicotinic acid NA stimulates release of prostaglandin D2 PGD2. To fully understand this mechanism, the investigators will examine the systemic release of PGD2 and skin blood flow using laser Doppler LDF on the upper and lower limbs of healthy control subjects. The investigators will quantify and establish the effects of oral nicotinic acid Niaspan given alone and in combination with aspirin on: 