There are two types: non-flush and flush Vitamin B3.

Niacin (vitamin B3) is a water-soluble B vitamin. It is found in supplements like multivitamins, prenatal vitamins, B complexes, and more. Niacin flushing is a side effect of taking higher doses of vitamin B3 supplements. It looks like red flushing on the skin. Sometimes it may also feel like itching or burning sensations.

Niacin (nicotinic acid vitamin), or vitamin B3, is an essential vitamin. Adults require a daily dietary intake of about 15 mg. At much higher doses (1000 to 2000 mg per day) niacin is used as a treatment for high cholesterol. These higher doses of niacin cause an intense flushing or "prickly heat" sensation to the face and upper body, usually 15-30 minutes after taking a relatively large dose (e.g. 500 mg). This flushing is experienced by almost everyone and, while it might feel like an allergy, it is not a true allergic reaction.

Other than causing discomfort the flushing is harmless and usually subsides within 1 or 2 hours. Symptoms are most intense after the first dose and typically diminish over days or weeks with continued use of niacin.

2:14 Is a Niacin Flush Harmful or Dangerous

4:37 BURN down the GLOW How Niacin fights radiation

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