You may have heard that you should wash your face with warm water to open up your pores – allowing the cleanser to penetrate deeper- and finish off with a cold rinse to close your pores. This theory comes from the idea that heat increases the kinetic energy of atoms, thus making the pore expand; vice versa for cold water.
To determine whether or not this theory is true, it’s important to first understand the biology of the skin.
Anatomy of the skin
The skin comprises three layers: hypodermis, dermis, and epidermis.
The hypodermis (subcutaneous layer) is the deepest layer in the skin that is responsible for simply storing connective tissue; consisting of collagen and elastin, these tissues work to repair wounds, store fat, and insulate. This layer isn’t technically considered part of the skin, as it primarily serves to connect and protect the body.
Above the hypodermis lies the dermis, which is responsible for fostering hair follicles, blood vessels, sebaceous glands, and sweat glands. The blood vessels support the function of the epidermis. The sebaceous and sweat glands lubricate the hair follicle, which then travels to and moisturizes the skin.
The outermost layer lies the epidermis, which is composed of cells that get gradually and naturally exfoliated by newer skin cells. This layer contains the stratum corneum, which is a layer that acts as a barrier for the skin, protecting it from outside irritants. Sweat glands, sebaceous glands, and hair follicles bleed into the epidermis to form openings on the surface of the skin. These openings are known as pores, which allow these glands to escape. The body has over 5 million hair follicles/pores!
Can pores open and close?
As pores are simply openings to hair follicles and glands on the epidermis rather than cells, the water temperature cannot expand nor contract pores. Pores do not have kinetic energy that responds to a change in temperature.
Luke-warm water is the best option
Given that the water’s temperature doesn’t directly open/close pores, it’s still beneficial to use warm water on your skin. Hot water damages cells called keratin on the epidermis, which can weaken and dry out the skin barrier. The high kinetic energy of the hot water will irritate/weaken the stratum corneum, ultimately drying it out and hampering its protection from irritants. Cold water, on the other hand, doesn’t damage the skin barrier; however, it still isn’t optimal when cleansing the face because it doesn’t dissolve the cleanser as well. Although cold water can reduce inflammation and increase blood circulation, by using lukewarm water, you’re receiving the benefit of faster-moving and more soluble water, while not damaging the epidermis. Warm water will optimize your cleanser’s ability to dissolve excess oil on your face.
As we’ve proved, the biology of the skin shows that pores can’t open/close in response to water temperature, since they are openings to the epidermis rather than cells. The appearance of congested pores is often confused with “open pores.” If you wish to target large, clogged pores, I recommend incorporating an exfoliating acid into your routine.
Bibliography
“Anatomy, Skin (Integument).” National Library of Medicine, 17 Oct. 2022, www.ncbi.nlm.nih.gov/books/NBK441980/#:~:text=The%20skin%20is%20primarily%20made,functions%20of%20the%20skin%20include. Accessed 18 Oct. 2024.
Hasudungan, Armando, composer. Introduction to Skin Anatomy and Physiology. 2019.
“Histology, Dermis.” National Library of Medicine, www.ncbi.nlm.nih.gov/books/NBK535346/#:~:text=The%20dermis%20is%20divided%20into,tissue%20that%20is%20highly%20vascular. Accessed 18 Oct. 2024.”In brief: How does skin work?” National Library of Medicine, www.ncbi.nlm.nih.gov/books/NBK279255/. Accessed 18 Oct. 2024.