The Ultimate Sunscreen Guide

Every single patient on YoDerm is recommended to apply sunscreen daily by her dermatologist, regardless of her skin-type, conditions, or treatments. The Doctors and Care Coordinators on YoDerm receive dozens of questions everyday about sun protection. Since we like to empower all of our patients with as much information as possible, we put together this post specifically for you to learn the fundamentals of sun protection. It’s a little long, but definitely worth your read. Drop a comment or shoot us an email if you want any more information or think we missed anything.

Sun Damage


The sun emits three types of ultraviolet radiation (UVC, UVB, and UVA). UVC rays are absorbed by the ozone layer and do not reach the Earth’s surface. However UVB and UVA rays penetrate the atmosphere and affect your skin in different ways.

UVA radiation causes tanning and premature aging
Ultraviolet-A (UVA) radiation penetrates the skin surface and hits the dermal and subcutaneous layers of the skin creating damaging reactive oxygen species (ROS). These photo-damaged cells spur melanin production in self-defense. More melanin makes your skin darker so it will absorb more energy towards the surface, protecting the deeper cells below.

The UVA energy’s ability to penetrate deeper into the skin also damages the underlying connective tissue and blood vessels. Over years of exposure, your skin loses its elasticity and starts to wrinkle. This is why UVA is considered the “aging” form of sunlight.

UVB radiation causes sunburns
Ultraviolet-B (UVB) radiation heats your skin cells. Your body’s natural defense to this heat is erythema (skin reddening) caused by your capillaries dilating to increase the blood flow in your skin. The increased blood flow helps cool your skin while also bringing necessary nutrients to the affected areas. This explains the reddening reaction that skin has to sun exposure, seen more easily in fairer skin.

Sunscreen: What’s Important

As explained above, the sun is your enemy; it has two weapons in UVA and UVB. UVA is always present and slowly chipping away at your skin’s health. Consistent application of an effective sunscreen is essential to your defense against the sun. Sadly, there’s a ton of confusion and misinformation out there about what effective really means. Below we have broken down the most important factors to consider when choosing your sunscreen.

The American Academy of Dermatology identified the three most important factors in choosing a sunscreen as:

  1. SPF 30+
  2. Broad spectrum
  3. Water resistant to at least 40 minutes

40% of products available on Walgreens.com do not meet the AAD’s minimum criteria.

SPF (Sunscreen Protection Factor)
SPF measures how well a sunscreen protects against UVB radiation. The minimal erythemal dose (MED) is the minimal dosage of ultraviolet radiation that causes a sunburn. SPF is defined as the MED ratio of unprotected skin to sunscreen protected skin. In laymen’s terms, skin applied with a sunscreen of SPF 5 will take 5 times as much time to burn as unprotected skin.

The American Academy of Dermatology recommends that you choose a sunscreen with a minimum of SPF 30.

Broad Spectrum Coverage
Broad spectrum coverage measures how well a sunscreen protects against UVA radiation. It is very important that you choose a sunscreen that says either “broad spectrum” or “UVA/UVB”. Without this, your skin will still be at risk of premature aging and skin cancer.

Water Resistance
Water resistance claims signify the product’s ability to protect your skin during and after swimming and/or sweating. There are now three categories for water resistance:

  1. No water resistance: products must include a warning on the back label to apply a water-resistant sunscreen if swimming or sweating.
  2. 40 minute water resistant claim
  3. 80 minute water resistant claim

If you are swimming or sweating in the sun, make sure to choose a sunscreen with at least a 40 minute water resistance claim and reapply accordingly. Remember that water resistant does not mean waterproof, which doesn’t exist. Reapply sunscreen when necessary or you’ll expose yourself!

Sunscreen Selector Tool Find the 3 Best Sunscreens For Your Skin


Picking the right sunscreen can be hard. As we touched on before, the easiest and most effective way to start your search is by looking for an SPF 30 (or higher) that is labeled “Broad Spectrum”. Beyond this rule of thumb, unfortunately, it becomes a lot more difficult to weed through the seemingly endless array of products.

The truth is there is no single perfect sunscreen for everyone. There are, however, some great options that can be near perfect in the right situations. We’ve developed a short quiz for you to take that will recommend 3 of the best sunscreens out there, tailored specifically to your skin type and lifestyle requirements. Give it a shot – the great thing about this quiz is there are no wrong answers.

Do you want an active, water-resistant sunscreen?



The 7 Laws of Sunscreen Application


1. Wear it everyday
Even when you’re not exposed to direct UVB rays, those UVA’s are always beating down on your skin. As we discussed earlier, UVA rays penetrate windows and clouds so it’s still necessary to apply sunscreen on overcast or indoor days.

2. Give yourself some prep time
Many of the sunscreens out there today have both physical and chemical filters: the active ingredients that stop the UV’s. The chemical filters must be absorbed by your skin before they’re effective so make sure you apply sunscreen at least 15 minutes before heading outdoors.

If you’re applying any other skin products (acne treatment, exfoliants, etc.) make sure to give them 15 minutes to be absorbed by your skin before applying sunscreen. If you’re applying makeup, apply the sunscreen first.

3. Apply liberally to all exposed body parts
We agree with the folks at Skinacea about how much sunscreen you should use. We’ve put together a table below for each body part. It seems like a lot..because it is. To effectively guard against UV’s you need at least 2mg of sunscreen per square centimeter of skin; the measurements below work out to about that amount.

Face: 1/4 teaspoon of sunscreen __ Neck (front and back): 1/4 teaspoon __ Arms: 1/2 teaspoon per arm __ Legs: 1 teaspoon per leg __ Chest: 1 teaspoon __ Back: 1 teaspoon

4. Pat don’t rub
Most people rub in sunscreen, but patting has many benefits:

  • Creates a uniform layer of sunscreen to give your skin surface equal protection
  • Reduces any irritation, particularly if you are breaking out
  • Gives your makeup an even surface to apply onto

5. Reapply
The AAD recommends that you reapply sunscreen every two hours, however this isn’t really specific enough. The following rules should cover when to reapply sunscreen.

  • After two hours: while outdoors, regardless of SPF or water resistance.
  • After you swim/sweat: depending on the water-resistance of the product which is either 40 or 80 minutes. If it’s not water-resistent, the product will have a warning on the back “to apply a water-resistent sunscreen if you’re swimming or sweating”
  • In the afternoon: if you applied in the morning and have spent the day inactive and indoors. Many people skip this, but your morning application will not give you adequate protection in the late afternoon, regardless of your day’s activites.
  • After a mid-day workout or shower: Many people forget to reapply if they workout or bathe and there is sunlight left.

6. Don’t forget the hands, ears, and neck
Self explanatory, but so many forget these areas!

7. Wash it off properly before bed
Sunscreen should be washed off before bed to avoid unnecessary pore clogging and/or irritation. Particularly if you struggle with acne or other blemishes.

More sun-protection tips


While sunscreen is the cornerstone of sun protection, the first line of defense is getting your lifestyle in check to minimize direct exposure to ultraviolet radiation. Make these changes and you’ll greatly reduce your likelihood of premature wrinkling and skin cancer:

  • Shady is the new Cool:
    Shade almost eliminates most direct exposure of UVB rays. At the beach, park, court, slopes, outdoor mall, or wherever…always seek shade or bring it with you.
  • Clothes are king:
    Reduce your risk by 27% by covering yourself with clothes. Opt for hats, long sleeves, and pants when you can.
  • Don’t get Burned:
    Your risk of melanoma doubles if you have had five or more sunburns. 42% of people reported getting sunburned at least once a year. Don’t be that guy.
  • DO NOT TAN!:
    There is no such thing as a healthy tan. And tanning early in life causes leathery, aging skin as early as your 30’s. Healthy is sexier than tan.
  • Rock Some Shades:
    Whether you’re rocking Jacky O’s or Oakley’s, sunglasses protect your eyes and shallow skin around them from UV’s.
  • Plan around the Primetime:
    Primetime UVB exposure occurs from 10am – 4pm. Plan your outdoor activities for the morning or late afternoon.
  • Get your Vitamin D safely:
    Your body creates Vitamin D from sun exposure, so if you’re awesome and integrating the tips above, you’ll need to get some D from your diet or supplements (600 IU is rec. daily dose).

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<image> When and Why You Should See A Dermatologist For Acne

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