Niacin

Vitamin B3, also known as niacin, is a food supplement with tremendous health benefits when taken in prescribed quantities. Vitamin B3 is one of the constituents of the multivitamin B-complex. Intake of vitamin B3 can sometimes cause an stomach upset. It is advisable to take the vitamin with food. Vitamin B3 can cause harmless flushing when used for the first time. Vitamin B3 is a naturally occurring substance found in meat, poultry, fish, eggs, and green vegetables. Vitamin B3 deficiency may cause pellagra, a disorder of the digestive and nervous system. 

Niacin contributes to normal energy yielding metabolism
Niacin contributes to normal functioning of the nervous system
Niacin contributes to normal psychological function
Niacin contributes to the maintenance of normal mucous membranes
Niacin contributes to the maintenance of normal skin
Niacin contributes to the reduction of tiredness and fatigue.

Nicotinic acid can causing flushing of the skin, especially in the hand and face region. This is a normal activity of niacin and is completely safe.