Common (1% to 10%): Pruritus, rash, sweating/hyperhidrosis, urticaria
Uncommon (% to 1%): Acne, alopecia, cold sweat, contact dermatitis, ecchymosis, eczema, increased tendency to bruise, maculopapular rash, skin discoloration, skin ulcer
Rare (less than %): Epidermal necrolysis/toxic epidermal necrolysis, erythema multiforme, furunculosis, hirsutism, petechia, photosensitivity reaction, psoriasis, purpura, purpuric rash, seborrhea, Stevens Johnson syndrome/Lyell syndrome
Frequency not reported: Erythema, exfoliative rash, heat rash, erythematous rash, follicular rash, generalized rash, macular rash, morbilliform rash, papular rash, pruritic rash, vesicular rash, umbilical erythema rash
Postmarketing reports: Erythema nodosum, exfoliative dermatitis, thrombocytopenic purpura [ Ref ]
One side effect of taking niacin supplements is mild flushing. Ross described it as a feeling of warmth, itching, redness or a tingly feeling under the skin. The flushing is harmless and usually subsides within one or two hours, according to the British Columbia Drug and Poison Information Center (DPIC). Some over-the-counter niacin tablets deliver the dose in a short burst, which makes the reaction more intense. Timed-release tablets deliver the vitamin more slowly, which reduces the intensity of the flushing. However, this type of niacin may cause liver damage in some people, according to the DPIC.