The relationship between ultraviolet (UV) radiation and sunburn is direct and biological—UV radiation causes sunburn by damaging the DNA and cells in the skin.
How UV Radiation Causes Sunburn:
- UVB is the Primary Cause:
- UVB rays (290–320 nm) penetrate the outer layers of the skin and directly damage DNA in skin cells.
- This triggers an inflammatory response, leading to redness, pain, swelling, and sometimes blistering—this is sunburn.
- UVA Also Contributes:
- UVA rays (320–400 nm) penetrate deeper into the skin.
- They generate free radicals that indirectly damage DNA and skin structures, accelerating aging and increasing cancer risk, but play a lesser role in causing sunburn.
- Immune and Inflammatory Response:
- The body reacts to the damage by increasing blood flow (causing redness) and sending immune cells to repair tissues.
- This inflammatory process produces the pain and heat associated with sunburn.
- Delayed Reaction:
- Sunburn symptoms typically appear 4 to 24 hours after exposure, peaking around 24–48 hours.
Severity Depends On:
- UV intensity (stronger at midday, high altitudes, near the equator)
- Duration of exposure
- Skin type (fair skin burns more easily)
- Lack of protection (no sunscreen, hats, or clothing)