I was prescribed niacin several months ago to lower my cholesterol. Weeks later I developed pain in my foot, also had some swelling of my face, hands and feet. I developed hives that itched, particularly if I exercised. All of these symptoms would come and go. I tried Benadryl, and my doctor put me on Medrol dosepack, but still kept me on the Niacin. Even though the Niacin was discontinued weeks ago, I still have some of the same problems. Tests for allergy to peanuts and shellfish were negative. I ate a few shrimp yesterday and exercised, and woke up today with hives that are itching; I feel fatigued and my skin feels uncomfortable. Could the Niacin I took still be causing this or did the Niacin trigger something in my body? I was never allergic to shellfish in the past. What else could be at work here?