How long does Azelaic acid take to work

[AlrightThen]

Im trying to get rid of post acne redness on my face, currently been using Azelaic Acid and Niacinimide daily, how long does this normally take to work and remove the marks, and should I start applying them twice daily?

 

[armenianpsycho77]

How long have you been using? 4-8 weeks is where you may start noticing less redness and more even skin tone.