At present, there is a plausible saying widely circulated:
Hot water can expand pores, while cold water can shrink pores. Wash your face alternately with hot and cold water, which can wash you cleaner and shrink your pores.
Stop it!
Alternating hot and cold water can really make the skin look firmer for the time being, but it is the blood vessels on the face that are more affected by the water temperature.
If you want to decontaminate and collect pores and wash your face with overheated and supercooled water, it will excessively stimulate blood vessels and be detrimental to the skin.
Especially for people with sensitive skin, cold and hot stimulation is likely to aggravate skin sensitivity.