Lightweight moisturizers for summer: Why even oily skin can get dehydrated

Even in the peak of summer heat, when skin appears shiny and sweats profusely, it can still be dehydrated. This apparent paradox occurs because increased surface hydration and sebum production do not necessarily indicate a healthy skin barrier. María Vicente and Virtudes Ruiz, cosmetic surgeons and formulators, explain that heat can boost sweat and oil production, making the skin seem well-hydrated. However, external factors like sun exposure, prolonged sweating, chlorine from pools, sea salt, air conditioning, and even frequent cleansing can disrupt the skin's lipid barrier. This disruption allows essential water to escape, leading to dehydration. A 2019 South Korean study published in the Journal of the European Academy of Dermatology and Venereology observed this phenomenon. Researchers found that after exposing 20 women to summer conditions, heat simultaneously increased surface hydration, sebum secretion, shine, and transepidermal water loss. The study highlights that skin's visible moisture and shine are not reliable indicators of its hydration levels. Many people forgo moisturizer in summer, seeking relief from the heavy feeling of creams mixed with sweat, sunscreen, and makeup. However, estheticians emphasize that skin doesn't 'breathe' through pores in the way commonly understood. The function of a moisturizer is to retain water in the outermost skin layer and prevent its loss, not to clog pores. Experts like Sílvia Giralt, an esthetician and cosmetologist, advise adapting skincare to the season, just as one would change clothing. She recommends lightweight textures that properly hydrate the skin, providing comfort in warmer temperatures. Xènia García, a beauty expert, notes that the sensation of heavy cream is often due to increased sweat and ambient humidity, making lighter formulations more suitable for summer.

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The heat can increase sweating, sebum production, shine, and apparent surface hydration. However, this does not necessarily mean that the barrier is in better condition.