The claims for niacinamide are pretty substantial and they are backed up by studies and good science. Studies have shown that 2% in a facial moisturizer can increase skin's keratin, ceramides, and barrier lipids which results in a reduction of transepidermal water loss (TEWL) and an increase in collagen synthesis. 2% can result in a 23% reduction in sebum production and pore diameter. It can reduce hyperpigmentation of age and sun spots. And it can reduce the damage from environmental causes, which reduces the irritation, inflammation, and skin redness from things like the sun, cold, or weather as well as application of straight SLS. Even at 5%, there's a lack of irritation and redness on our faces ('cause sometimes niacin can make our skin flush, but not at 2% or 5%). It can reduce the appearance of fine lines and wrinkles and decreases skin blotchiness and "pebbling" or roughness on facial skin. It also behaves as an anti-inflammatory and enhances skin's barrier functions.
All of these great things can happen in a short period of time. In one study, all of these results were seen within 12 days (the first time they checked, so it could have been a shorter period of time) and continued to work with application of the moisturizer daily.
Use it in your heated water phase or cool down phase, but make sure you dissolve it well. I've had no problems dissolving this ingredient and no problems with precipitation after it has dissolved.
cucumber extract toner at 2% and absolutely love it! You can use it in a facial moisturizer - try it as the only active to make sure your skin likes it - or an oil free facial moisturizer for oily skin. It is water soluble, so you can only use it in things that contain water or water soluble ingredients. Sorry, lotion bars or balms are right out!
Handbook of Cosmetic Science & Technology (textbook)
Surfactants in Personal Care Products and Decorative Cosmetics (textbook)