Which type of sunblock should I use to prevent acne and oily face?

I noticed that I tend to breakouts after holidays. Yes, weather and humidity changes can sometimes trigger breakouts. Stress/poor quality of sleep due to jet lag and time differences can also contribute. Speaking from personal experience here; I tend to break out much worse in Singapore than I did living in the UK. Went to national skin centre for consultation, and was given some watery creams and Cetaphil products to use. Hard to comment on what you were given, but from what you’ve described here, NSC doesn’t seem to have given you anything specifically for acne treatment.

I would recommend you have a detailed talk with your doctor on the timeline and history of your outbreaks. Adult onset acne is a common occurrence and can be due to issues ranging from hormonal issues, change in skincare as you mentioned, or even undiagnosed medical conditions. Treatment then depends on the underlying problem. Initial treatment to reduce sebaceous gland activity and reduce acne occurance and the other issues that follow, such as scars and redness, can be managed with techniques ranging from lasers and peels to oral medication.