toggle mobile menu Menu
toggle search menu

Site Navigation

Supplemental

Menu

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 ofJune 26, 2019

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

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Healthwise is a URAC accredited health web site content provider. Privacy Policy. How this information was developed to help you make better health decisions.

© 1995-2015 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.