Heya Wei,
To add on to Dr Ethan's good suggestions:
1. Regular clay masking can help prevent sebum build-up.
2. AHA or BHA Acid toners used once to twice daily help keep enlarged pores and excessive oil production in check.
3. Differin and retin can actually now be purchased from your local pharmacy without a prescription. I would, however, still consult a doctor about its use as it can be irritative to skin, especially when used in combination with other over-the-counter products containing low dose acids or retins. Furthermore, its use in certain populations (such as pregnant patients or those trying to conceive) is not recommended.
At the end of the day, do realise that pores are the living, breathing units of your skin - its a never ending cycle so maintenance is key!
Best,
Shane
