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What SPF sunscreen should I use?

Nicole needs to know…Is there a really big difference between using SPF 15 and SPF 30 facial moisturizer? If so, why? I was told to wear 30 in order to prevent rosacea flare ups.

The Beauty Brains replysun-32198_1280

Skin exposure to UV rays is almost never good for the skin. It causes sun burn, wrinkles, dryness, and as you’ve implied, rosacea flare ups. This is why the most important thing you can do for your skin is to wear a sunscreen or stay out of the sun. But what kind of sunscreen should you use?


Before answering this, we should first tell you what the SPF number means. SPF stands for sun protection factor and it essentially is a rating of how much UV light will be blocked. In general, a higher SPF number offers more protection from UV exposure than a lower number. How effective it is depends on many factors but the number one factor is your skin type. SPF 15 means that if you would normally burn after being in the sun for 20 minutes, you will be able to stay in the sun for 15 times as long or 5 hours. But it is important to note that the SPF scale is not a linear one. An SPF 2 will block 50% of the UV light while an SPF 15 will block 92% of all the UV light that reaches your skin and an SPF 34 blocks 97% of the UV light.

SPF effectiveness

Although skin type is the number one factor is determining the effectiveness of a sunscreen, it is not the only factor. The intensity of the sun and the amount that you apply is also important. It’s this second factor that is most relevant to your question.

SPF 15, 30 or more

For cosmetic chemists, creating a great sunscreen is a balance between making a product that is effective and making one that feels good on the skin. If it were just a matter of effectiveness, everyone would create SPF 50 products or higher. But the problem with creating a higher SPF product is that for each number you go up, you increase the greasy, nasty feel on your skin. An SPF 15 feels much better than an SPF 30. And an SPF 100 is, well, gross.

Of course, the point of a sunscreen is to protect you from UV damage so you need to use an SPF sunblock with a high enough number to give you good protection.

SPF experts

Experts at the FDA have suggested that an sPF 15 is the minium that you should be using to protect your skin from UV damage. In testing these sunscreens have been shown to provide adequate protection when combined with limiting your time in the sun, wearing sun protective clothes. And an SPF 15 also can be made so it doesn’t feel excessively greasy.

SPF 15 is not enough

While the experts say SPF 15 scores high enough in testing to give protection, that is only true if you are applying the right amount. In testing, scientists use 2 mg/cm2 of skin. So, do people apply this much?

In a word…no. It is well known that people typically apply much less than the amount tested by sunscreen manufacturers.

Think about how much you use. If you were applying 2 mg/cm2 of sunscreen, your skin should feel greasy, slippery, and some of the sunscreen will be running off your skin. For an average sized person, you would need to apply about 30 mL of sunscreen per application. One bottle wouldn’t even be enough for a week at the beach.

1/3 effective

So, while technically an SPF 15 will work (and it’s certainly better than nothing), it requires much more than you apply now. A good rule of thumb is that your sunscreen will be 1/3 as effective as the number based on the way people typically apply the product. That means an SPF 15 will protect you like a lab tested SPF 5. An SPF 30 will give SPF 10 protection in real life application.

Therefore, unless you going to glop on a lot more SPF sunblock than you are using now, you should stick with an SPF 30 or higher. This will give you the best chance at preventing sunburns and UV induced rosacea flare ups.

For more information on sunscreen effectiveness see the following resources
1. Melanoma foundation facts about sunscreens.
2. FDA Sunscreen guide
3. National Institute of Health and Clinical Excellence Skin cancer prevention report
4. Dr. Steven Wang – Sunscreen Guide

If you need to purchase sunscreen, please shop using this link and you’ll be supporting the Beauty Brains.


Comments on this entry are closed.

  • gabis February 21, 2015, 6:17 pm

    I have a question not exactly related to this post but to the topic anyway. So I was told vegetable oils have natural sunscreen protection. There’s even a picture (in portuguese though): http://1.bp.blogspot.com/-M5z1o8SdR7U/UpQTbbI8L-I/AAAAAAAABBs/rRcdTPt8k54/s1600/1185075_577947222267296_864540784_n.jpg. Can these vegetable oils really help against UV rays? Or are people mistaking heat resistance for sun blocking?

  • Eileen February 23, 2015, 12:31 pm

    Something that was not mentioned, but which I feel is crucial, is that for many rosacea sufferers such as I, the use of chemical sunscreens is out of the question. We can only tolerate the physical sunscreens titanium dioxide and zinc oxide. Fortunately for us, there are some outstanding physical sunscreens that are transparent (don’t leave a white caste), cosmetically elegant (glide over the skin easily and play nice with skincare products and makeup), and offer adequate protection (SPF 30 or higher). Unfortunately, those excellent sunscreens don’t come cheap and so I stock up on my preferred brand twice a year during my dermatologist’s patient appreciation days. Yes, I spend more on sunscreen than the average person, but the comfort, appearance, and overall health of my rosacea prone skin is important to my well-being. As for those cheap ones in the drugstores and
    markets, they’re terrible and give physical sunscreens a bad name because they’re “greasy”, “nasty”, and “gross” (Gotta love your scientific terminology! LOL).

    • Anna September 1, 2017, 10:46 pm

      Hi Eileen, what sunscreen do you use? I am having a hard time finding one. (Sorry, I know this is two years after you posted!)

  • Lan February 26, 2015, 3:10 pm

    I use Blue Lizard Sensitive Sunscreen and I use it about every day. It has 10% Zinc oxide and 6% Titanium Dioxide. It’s chemical-free, Paraben free and really has no scent, which is important to me. You can get it right from their website: http://www.bluelizard.net Hope this helps!

  • Audrey May 31, 2016, 2:12 am

    Is there any benefit to using a physical sunscreen instead of a chemical sunscreen? Why or why not?

    • Randy Schueller May 31, 2016, 8:20 am

      Some people find physical sunscreens less irritating. Others find that chemical sunscreens leave less of a visible residue.

  • Yori Bracket October 7, 2016, 6:28 am

    Does this apply to people of colour?

  • Shevan Qawouq April 2, 2017, 6:12 pm

    What is the amount of Zno and Tio2 for sunscreen
    Thank you

  • Rochelle Broder-Singer May 21, 2017, 12:32 pm

    Drunk Elephant makes a great broad-spectrum physical-only facial sunscreen moisturizer. It’s expensive, and it feels wonderful on my sensiiev, dry skin. It’s called Umbra. Josie Maran’s facial moisturizer/sunscreen is also all-physical, broad-spectrum and feels wonderful on my sensitive, dry skin.