For consistently clear skin, we recommend a professional facial cleansing every 4–6 weeks. Depending on your skin condition, shorter intervals of 2–4 weeks may also be beneficial for blemish-prone or acne-prone skin.
Regular professional facial cleansing treatments support skin renewal, help keep the pores clean and improve the appearance of the skin over the long term. Scientific research also shows that the outermost layer of the skin renews itself approximately every 28 days, which is why regular treatments at similar intervals may be beneficial.
Source: The Epidermal Renewal Process –
https://www.ncbi.nlm.nih.gov/books/NBK26865/