Skip to Content

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

ByHealthwise Staff
Primary Medical ReviewerWilliam H. Blahd, Jr., MD, FACEP - Emergency Medicine
Adam Husney, MD - Family Medicine
Kathleen Romito, MD - Family Medicine
Specialist Medical ReviewerE. Gregory Thompson, MD - Internal Medicine

Current as ofNovember 20, 2017

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 and Privacy Policy. Learn how we develop our content.

© 1995-2018 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.

Symptom Checker

Feeling under the weather?

Use our interactive symptom checker to evaluate your symptoms and determine appropriate action or treatment.

Symptom Checker

Decision Points

Our interactive Decision Points guide you through making key health decisions by combining medical information with your personal information.

You'll find Decision Points to help you answer questions about:

Interactive Tools

Get started learning more about your health!

Our Interactive Tools can help you make smart decisions for a healthier life. You'll find personal calculators and tools for health and fitness, lifestyle checkups, and pregnancy.