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Ultraviolet Rays From the Sun

Topic Overview

The sunlight that reaches the earth has ultraviolet A and ultraviolet B (UVA and UVB) rays. These ultraviolet rays are the main causes of damage to the skin from the sun. UVA and UVB rays affect the skin's sensitivity to sun exposure in different ways.

UVA:

  • Can pass through window glass.
  • Is not affected by a change in altitude or weather.
  • Is present all day and every day of the year.
  • Penetrates deep into skin layers.
  • Is 20 times more abundant than UVB rays.
  • Causes long-term skin damage.

UVB:

  • Cannot pass through window glass.
  • Causes sunburn.
  • Causes tanning.
  • Helps the body make vitamin D.
  • Is more intense:
    • During the middle of the day.
    • In the summer.
    • At high altitudes and near the equator.
  • Can cause skin cancer and cataracts.

Protect your skin

Protect your skin from too much sun when outdoors.

  • Seek shade from 10 a.m. to 4 p.m.
  • Cover up with a wide-brimmed hat and tightly-woven clothing.
  • Wear UV-blocking sunglasses.
  • Apply broad-spectrum sunscreen on any exposed skin, even when it's cloudy. Use SPF 30 or higher. Reapply as needed.

Credits

Current as of: July 1, 2021

Author: Healthwise Staff
Medical Review:
William H. Blahd Jr. MD, FACEP - Emergency Medicine
Adam Husney MD - Family Medicine
Kathleen Romito MD - Family Medicine
E. Gregory Thompson MD - Internal Medicine

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