十万个为什么·科学启蒙30篇（1）

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晒伤时身体发生了什么？

Sunburn is your skin’s inflammatory reaction to damage caused by ultraviolet (UV) radiation from sunlight or tanning beds.
UVB rays directly harm DNA in skin cells, triggering repair mechanisms and sometimes causing mutations that lead to skin cancer.
UVA rays penetrate deeper, breaking down collagen and elastin fibers that keep skin firm and youthful.
Within minutes of exposure, blood vessels widen and immune cells rush to the area, causing redness, warmth, and swelling.
Dead or damaged skin cells begin peeling off after a few days as your body replaces them with fresh layers.
Melanin—the pigment that gives skin its color—increases in response to UV, causing tanning, but this offers only minimal natural protection.
People with fair skin, light eyes, or many moles have less built-in melanin defense and burn more easily.
Severe sunburns blister because fluid leaks into upper skin layers, separating them from the deeper tissue beneath.
Repeated sunburns before age 18 double the risk of developing melanoma later in life.
Broad-spectrum sunscreen blocks both UVA and UVB, and reapplying every two hours ensures continuous coverage during outdoor activity.