Using HEC with Salicylic Acid, Niacinamide and Azelaic Acid? CurlBlog General Using HEC with Salicylic Acid, Niacinamide and Azelaic Acid? curlytea August 15, 2023 I got an email question about formulating with HEC (hydroxyethyl cellulose), salicylic acid, niacinamide and azelaic acid.... Read More Read more about Using HEC with Salicylic Acid, Niacinamide and Azelaic Acid?