Hi,
As a general guide, an interval of 10-15mins between application of different layers of creams is recommended.
Hence, extrapolating to the situation asked, it may be best that retinol is applied 10-15mins after use of toner rather than immediately after. This is to avoid potential interaction between the 2 products which could possibly increase skin irritation or decrease the effects of the retinol.
Hope this suggestion helps!
