Here's a more detailed explanation:
* Pores and Hair Follicles: The "pores" people often refer to on their scalp are actually hair follicles. Each hair grows from a hair follicle, which also contains sebaceous glands (oil glands).
* Heat and Cleansing: Warm water and shampoo can soften sebum (oil) and loosen dirt and debris within the hair follicles. This can make the follicles *appear* more open because they are clearer and less clogged.
* Pore Size and Temperature: Pores themselves don't have muscles to actively open and close in the same way that, say, blood vessels do. Extreme temperatures can cause the skin around pores to swell or shrink, which might make them look larger or smaller temporarily. However, the actual pore size remains relatively constant.
* Benefits of Washing Hair: Washing your hair helps remove excess oil, dead skin cells, and product buildup from the scalp. This can prevent clogged follicles, which can lead to issues like dandruff or folliculitis.
In Summary:
While washing your hair might make your hair follicles *appear* more open due to the removal of debris, it doesn't fundamentally change the size or structure of your pores. The cleansing action helps keep the hair follicles clear and healthy.
If you have concerns about your scalp or hair follicles, it's best to consult with a dermatologist or trichologist.