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Everything You Need to Know About Sunscreen & Using it Properly

June 5, 2019 by dermlagrange

Sunscreen is one of the best life-saving products you can use. However, knowing the differences between different types and how to choose one that’s best for you is the most important thing.

And here to teach us more about sunscreen is Caitrin Standring, PA-C.

Learn from Caitrin Standring, PA-C

Caitrin is a Board-Certified Physician Assistant in Dermatology. She completed her undergraduate studies at the University of California Santa Barbara, earning a Bachelor of Science in Mechanical Engineering. Caitrin then attended graduate school and received her Masters of Science in Physician Assistant Studies from Concordia University of Wisconsin.

Prior to joining our practice, she worked as a Board Certified Physician Assistant in Dermatology at a private practice in downtown Chicago and the northwest suburbs. Caitrin is trained in cosmetic, medical, and surgical dermatology, and manages a full spectrum of dermatologic conditions. Her professional memberships include the Society of Dermatology Physician Assistants and the Illinois Society of Dermatology Physician Assistants.

What is the difference between physical and chemical sunscreen?

Sunscreen prevents damage to the skin by absorbing, reflecting, and/or scattering ultraviolet (UV) radiation. There are a few key differences between physical and chemical sunscreen formulas.

Physical sunscreen (also referred to as mineral based sunscreen):

  • Active ingredients are minerals: zinc oxide, titanium dioxide
  • Sits on top of your skin and protects it by reflecting UV rays away from your body, providing a physical barrier between the sun’s rays and your skin
  • Typically less irritating than chemical sunscreens
  • Can be more difficult to blend into the skin than chemical sunscreens

Chemical sunscreens:

  • Active ingredients are chemical compounds: octinoxate, avobenzone, oxybenzone, homosalate, octisalate, octocrylene
  • Absorbs into the skin and absorbs the sun’s UV rays, which are then converted to heat and released from the body
  • Can cause skin irritation in those with sensitive skin
  • Typically absorbs more quickly into the skin than mineral-based sunscreens

How do I choose a sunscreen?

Finding the right sunscreen for you is super important because not all versions of sunscreen will react well with all skin types.

Here are my tips for how to choose a sunscreen:

  • Sunscreen should have broad-spectrum coverage, meaning protection against both UVA and UVB rays.
  • If you have oily or acne prone skin, I recommend using a non-comedogenic (meaning it won’t clog pores), oil-free sunscreen.
  • If you have sensitive skin, or for children and babies, I recommend using a physical/mineral based sunscreen containing only zinc oxide and/or titanium dioxide.
  • If you are swimming, playing sports, or sweating a lot during the day, it is important to use a water-resistant or waterproof formulation.


types of sunscreen

What SPF should I use?


SPF (sun protection factor) is a relative measure of how long a sunscreen will protect you from UVB rays.

The SPF factor works like this: whichever number SPF you get allows you to stay in the sun that amount of times longer without burning than you normally would. So if you normally burn after 30 minutes and use an SPF 15 sunscreen, you will be able to stay in the sun for 7.5 hours without burning (provided you used the product properly and reapplied when necessary).

I always recommend using a broad spectrum sunscreen, one that protects against both UVB and UVA rays, with at least SPF 30 or greater and to always follow your sunscreen’s application directions.

When should I apply sunscreen?


Sunscreen should be applied 15-30 minutes before sun exposure in order to provide optimal protection.

When outdoors, sunscreen should be reapplied every one to two hours (especially if swimming or sweating a lot). Remember to apply sunscreen to your ears and don’t forget to also apply a lip balm with SPF 30 or higher to protect your lips.

Do I really need to apply sunscreen every day?


Yes. I believe everyone should apply a daily moisturizer (or sunscreen) with at least SPF 30 to their face, neck, ears, and backs of the hands before heading outdoors.

Many people don’t realize that exposure to harmful ultraviolet radiation from the sun can occur even when it’s overcast and cloudy, while riding or driving in a car, or through windows. Temperature is unrelated to potential damage to your skin by UV rays, so be sure to apply daily sun protection year round, winter or summer.


Remember that sunscreen can only do so much. In general, try to avoid direct sun exposure between the hours of 10 AM and 4 PM, when the sun’s UV rays are the strongest.

Seek shade and wear sun protective clothing whenever possible and book regular skin-checks at your dermatologist!


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