The Langerhan cells are responsible for the skin's immune response.
In a strong and healthy skin, we would see a large number of Langerhans cells, all with long dendritic arms, which provide very effective protection from bacteria, pathogens and irritants.
However, in inflamed skin, we often see an impaired skin immune function, where there are fewer Langerhans cells with damaged shortened arms. This greatly reduces the effectiveness of the skin's immunity and leads to excessive immune responses to small threats.
To strengthen the Langerhans cell function, topical Niacinamide (Vitamin B3) works as a tonic for the Langerhans cells to become stronger and to re-lengthen their dendritic arms.
For a boost of Niacinamide, I recommend you try the Aspect Extreme B 17.