Summer skincare — the triple threat of UV, sweat, and sebum

Summer is the toughest season for skin. UV rays, sweat, and sebum — three risks converge simultaneously, compounded by air conditioning dryness. Let's understand the proper countermeasures for each.

UV — reapplication every 2 hours is key

Sunscreen doesn't last all day from a single morning application. Sweat and sebum reduce its effectiveness within 2-3 hours. In summer, reapplying every 2 hours is fundamental. "SPF30 reapplied every 2 hours" is more effective than "SPF50 applied once in the morning."

NMF (Natural Moisturizing Factors) lost through sweat

When you sweat, the NMF (Natural Moisturizing Factors) in the stratum corneum — amino acids, urea, sodium lactate — are washed away. That tight feeling after sweating is because NMF has been lost and the stratum corneum's water-holding capacity has decreased. This is precisely why moisturizing matters in summer.

The sebum trap — "oily skin" does not mean "hydrated skin"

Sebum production increases with rising temperatures in summer. While the skin surface feels oily, leading many to think "I'm moisturized enough," sebum is an "oil seal," not "water supply." More sebum does not mean the skin's interior is hydrated.

The air conditioning trap

Indoor humidity can drop below 40% in summer due to air conditioning. Sweating outdoors, then drying out indoors — this constant cycle weakens the skin's barrier function.

Choosing lightweight textures without sacrificing moisture

In summer, choose products with lightweight textures but strong moisturizing power, such as gel types containing hyaluronic acid or ceramides. "Refreshing" does not necessarily mean "low moisturizing power." Texture and hydration capacity are two different axes.