Niacinamide + Tretinoin: can you use them together?

There is a persistent myth circulating that you cannot use niacinamide and tretinoin together because niacinamide converts to niacin which can cause flushing. This is based on a very old in-vitro study that used extreme concentrations at high temperatures — conditions that have nothing to do with topical application.

In real-world use, niacinamide and tretinoin are not only compatible, they're actually a good combination. Niacinamide helps maintain the skin barrier, reduces transepidermal water loss, and calms the irritation that tret can cause. Several dermatologists actively recommend combining them.

You can apply them in the same routine. My personal method: gentle cleanse, wait until dry, apply a niacinamide serum (I use The Ordinary 10% or Paula's Choice 10%), wait 5 minutes to let it settle, then apply tretinoin. Moisturise on top. The niacinamide pre-application actually buffers some of the dryness associated with tret.

Alternatively, some people do niacinamide in the morning routine and tret at night, which also works fine.

The only thing I'd avoid is using a niacinamide + acid combo at high concentrations directly alongside tret in the same step — unnecessary stacking, not dangerous but not adding value either. Keep the routine simple.

Worth noting the niacin flushing concern was also largely about oral niacinamide, not topical. Topically, even if trace amounts of niacin were produced, the systemic absorption is too low to cause any meaningful reaction. The chemistry just doesn't hold up at physiological temperatures on skin.

This is reassuring. I've been keeping them in separate routines just to be safe but I'll try using niacinamide before tret at night and see if it helps with the dryness I've been getting.

What concentration of niacinamide do you recommend? I see everything from 2% up to 20% and it's hard to know what's actually useful vs just marketing.

Studies show benefits from 2% upwards. 5% is the most well-studied for hyperpigmentation and barrier function. Anything above 10% has diminishing returns and may increase sensitivity in some people. I'd stick to 5-10%. The Ordinary's 10% is fine for most people, Naturium's 12% is a bit much. Paula's Choice 10% is probably the best formulated one I've tried.