How SPF Ratings Work

Get 20% off sunscreens throughout April 2019 at UW Health Jeune Skin Care locations

If you're uncertain about what the SPF number stands for in your sunscreen, you're not alone. The Sun Protection Factor system (SPF) measures the length of time a sunscreen will protect your skin from burning and becoming red from ultraviolet B (UVB) rays, compared to how long it would take your skin to burn without any sunscreen protection.


To determine the protection level of a sunscreen, multiply the SPF rating on the bottle by the amount of time it takes your skin to develop burning/redness from the sun. This will vary from person to person.


If it takes 10 minutes without any sun protection for your skin to begin reddening, using an SPF 15 would theoretically prevent reddening 15 times longer (10 x 15 = 150); 150 minutes or 2 ½ hours.


Using an SPF 30 would give protection 30 times longer (10 x 30 = 300); 300 minutes or 5 hours.


To maintain SPF, reapply sunscreen every 2 hours (even with high SPF) and right after swimming. The Skin Cancer Foundation recommends SPF of at least 15, which blocks 93% of UVB rays. While SPFs higher than 30 block only 4% more UVB, it may be advisable for sun-sensitive individuals, skin cancer patients, and people at high risk for developing skin cancer.


Remember that the current rating system only applies to UVB rays. It is important to find a "broad-spectrum sunscreen," meaning it shields against most types of ultraviolet rays, UVA as well as UVB.


Look on the label for these UVA protecting ingredients:

  • Zinc oxide
  • Titanium oxide
  • Avobenzone

To Sum Up


It is best to find a broad-spectrum SPF of 15 or greater and reapply every 2 hours.


April Discount: 20% Off Sunscreens


Throughout April 2019, get 20% off our sunscreens:

  • Obagi Sun-Shield Matte Lotion SPF 50
    $53.00* regular price; $42.40* discount price 
  • Revision Intellishade Original Tinted Moisturizer SPF 45
    $75.00* regular price; $60.00* discount price 
  • Revision Intellishade Matte Tinted Moisturizer SPF 45
    $75.00* regular price; $60.00* discount price 
  • SkinCeuticals Physical Eye Defense SPF 50
    $30.00* regular price; $24.00* discount price 
  • SkinCeuticals Physical UV Defense SPF 30
    $34.00* regular price; $27.20* discount price 
  • SkinCeuticals Sheer Physical SPF 50
    $34.00* regular price; $27.20* discount price 
  • SkinMedica Total Defense SPF 34
    $68.00* regular price; $54.40* discount price

Jeune Skin Care offers a variety of broad-spectrum sunscreens. Our medical aestheticians can help determine what best fits your needs.


Jeune Skin Care Locations


2349 Deming Way in Middleton:

  • Monday and Wednesday: 8am-7pm
  • Tuesday, Thursday and Friday: 8am-5pm 

20 S. Park Street in Madison:

  • Monday-Friday: 8am-5pm