Benadryl Niacin interaction

I recently blacked out and suffered a head injury while taking Niacin (first time) the day after I had taken prescription Benadryl for an insect sting that swelled up. Is this a commonly known drug interaction? Niacin is just Vitamin B3, so why does it act like this? I felt as if my whole body was on fire. That's the last time I take Niacin. Has anyone else had this problem?

[Paderla Anitha, DNB]

Hello and hope you are doing well.

Niacin does interact with other medications namely aspirin, calcium supplements, lasix and tylenol to name a few. But it is unlikely to interact with benadryl. Black outs may happen if there is inadequate supply of oxygen to the brain. This can happen with cardiac disorders or lung disorders. Again inadequate sleep, hypoglycemia, anemia and vitamin deficiencies can aggravate you symptoms. You will need to consult your primary care physician for a proper evaluation.

Hope this helped and do keep us posted.