It is one of the mildest molecules suitable for all skin types and has clinically shown no significant side effects. However, as Niacinamide causes skin turnover, some people might experience purging, especially when using a highly concentrated product like this one. Purging is a natural phenomenon wherein your skin adjusts to the new active, especially the ones that increase cell turnover. It may not last for more than 2-3 weeks depending upon your skin condition and regimen.