How Often Should You Reapply Mineral Zinc Oxide Sunscreen?

How often should you reapply mineral zinc oxide sunscreen? Do you know? You hear that you need to reapply sunscreen every 2 hours. Does that apply to ALL sunscreens? You also have heard that mineral sunscreens are better, may be less fragile than chemical sunscreens and you also know that reapplying sunscreen is really inconvenient. I want to share this exact question that was sent in by a reader. 

Dermatologist answers the question, "Does mineral sunscreen need to be reapplied?"

Hello Dr. Bailey,

You have the BEST information on your website, and I have learned a lot from your blogs. Thanks so much for writing them!

I have recently purchased the Citrix SPF 40 sunscreen. It is the first zinc oxide sunscreen I've found that doesn't turn my face ghost white! I have read about your use of that product.

I have a question on frequency of applying it to my face/neck. Do you think it lasts longer than sunscreens that just rely on chemical reaction on the skin? I put the Citrix product on my face early in morning, and wonder if it has "some" protection even later in the day, albeit probably less protection. I work inside in an office, so during week I'm only exposed during lunch and again on the drive home. Do you think I should keep re-applying it?

Chuck G

Hello Chuck,

I am glad you like the Citrix Sunscreen. My family and I have used it for years! It is a really excellent sunscreen - it has protected us well and for that I am deeply grateful to our chemist who created it. Your question about what “rules” apply for reapplication of a mineral zinc oxide sunscreen is a really important one. I want to provide a really thorough answer because sun protection is the number one skin care step for keeping your skin healthy throughout your life.

As your question infers, the need for reapplication depends on the amount of sun exposure and the type of sunscreen.  First let's talk about zinc oxide versus chemical sunscreens.

What is the difference between a mineral zinc oxide (physical) sunscreen and a chemical sunscreen?

Mineral zinc oxide sunscreen works by bouncing UV rays off your skin. It bounces almost the full spectrum of UV rays off, which is why I prefer this ingredient to all other sunscreen ingredients, including titanium dioxide.

In the process of bouncing UV rays away from you, some of the zinc oxide particles will eventually be broken down and lost. This loss is nothing compared to the loss of chemical sunscreen molecules, which are designed to be lost as part of their UV protective mechanism. Interestingly, this mechanism of chemical sunscreen action also generates heat as part of the chemical reaction that prevents the ray from entering the skin. Have you ever noticed feeling hotter than expected when wearing chemical sunscreen?

I am not a fan of the chemical sunscreen mechanism of action. The good news is that we now have entirely invisible mineral zinc oxide sunscreens that are lightweight and easy to use. - Dr. Bailey

My collection of sunscreens consists of only products that use the latest transparent zinc oxide technology.

Select from the invisible SPF 50+ sunscreen products including:

The Sheer Strength Pure Physical Facial Matte Tinted SPF 50 Sunscreen  provides water resistant protection that includes over 3.2% iron oxide to block visible light and blue digital light that both can darkening pigment skin problems. I recommend this product for people struggling with facial pigment skin problems such as melasma, sun spots and brown acne marks.

Sheer Strength Pure Physical Invisible SPF 50 Sunscreen is ideal for those people wanting a weightless and untinted daily face SPF. Men love this product because it rubs in easily to the beard area. 

Both Sheer Strength Pure Physical facial sunscreens are fragrance-free, are not greasy, won't clog pores, and they work beautifully under makeup.

My sunscreen collection also includes water resistant SPF 40 Citrix Sunscreen that provides invisible zinc oxide broad spectrum sun protection. 

My patients, family and I have used Citrix for years. We've put this product to the test and it has continued to protect our skin day after day. Reader Chuck has discovered how easy Citrix is to use. What is important is that is also works great and is my go-to daily wear sunscreen product for my neck, back of my hands and any other exposed skin. I wear it gardening, swimming, hiking etc. 

Wearing a sun protection hat will help your sunscreen last longer. 

Wear a full brim UPF 50 hat to shade your face. There will be less 'direct strikes' from UV rays on to your protective layer of sunscreen. Thus, your sunscreen will theoretically last longer since all sunscreens break down when they deflect UV rays! It's a simple trick. My Sunscreen and Sun Protection Collection includes a great women's UPF 50 bucket hat that is convenient, dependable and affordable.

It is important to know that zinc oxide particle breakdown is slower than chemical UV filter breakdown. I like to think of it as you get more “wear and tear" from your zinc oxide product than a chemical product. Just how much we don't know, but this is how the two categories of UV filters work. My opinion is that you don't need to reapply mineral sunscreen as urgently as you do chemical sunscreen based on what we know about their mechanisms of action. That said,

If you are in intense sun and depending on zinc oxide sunscreen alone to protect your skin then you will need reapplication and you better err on the safe side of the 2-hour rule. - Dr. Bailey

Sunscreen on your skin also migrates. Have you noticed that you see it accumulate in skin creases like those on your neck? It is another reason why you want to reapply sunscreen when you are depending on it for protection.

The 'wear and tear' on your zinc oxide sunscreen by intense UV ray bombardment, and the migration of product on your skin is why we recommend adding some help for your sunscreen such as using a sun hat, standing in the shade, or remaining indoors for many of those daylight hours.

I have great dermatologist-approved hats, sunscreens and even a small UV sensing keychain on my Sun Protection Products page to help you sun protect your skin.

Chuck, this combined sun protection strategy sounds like what you are doing! Well done for wearing sunscreen daily even when you expect to be indoors a lot!

So, when sunscreen is used alone for protection of all-day sun exposure, I tell my patients they need to follow the “rules” and reapply even a physical sunscreen with mineral zinc protection every two hours. One easy way is to monitor this is to time reapplication with a rest period such as lunch. Sunscreens also always need to be reapplied after sweating, rubbing, or swimming too.

If, however, a person is in a less intense UV exposure scenario, such as when they are indoors a good portion of the day and/or they are in the shade or wearing a full hat when outside, then the sunscreen’s zinc oxide particles may well last all day. It’s not hard to tell because skin gives us good feedback information.

Know that when a sunscreen is not adequately present on your skin before UV exposure, your skin will tan and age spots will darken.

If this happens, you know that you need to increase your sun protection measures!

In my life, I have used myself as a handy 'guinea pig' to test sunscreens. My fair Type 2 skin will show a darkening of its age spots if I don’t work really hard to prevent that from happening. On the average day, a good application of zinc oxide sunscreen, being mostly indoors and wearing a hat or being in the shade when outside will entirely prevent my age spots from darkening without needing to reapply sunscreen. If, however, I’m gardening in the sun for hours, wearing a hat, working in the shade when possible but sweating, getting lots of sun (including rays reflected off of pavement or stucco walls), then I need to reapply sunscreen at least midday. If I don't reapply sunscreen then my age spots darken, and my skin may even feel a little sensitive in the evening.

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How do you decide if you need to reapply your zinc oxide sunscreen? 

Ask yourself these questions:

• How much sunscreen do you initially apply? Is it enough? (I’ve found that the average size face with a full head of hair needs about 1/3 tsp. But this does not include the neck, ears, part line or bald scalp, etc.)
• How high is your sunscreen's SPF? I have the best broad spectrum SPF 30+ zinc oxide sunscreens. Click here to see the products I trust. 
• What are your activities for the day? Will you be in the direct sun for hours or will you be mostly inside, or just running a few outdoor errands?
• Are you also applying mineral makeup? It can help to give extra protection.
• Where on the earth will you be and how intense are the UV rays? Are you on the equator or in Norway during the winter?
• Do you sweat a lot and wash off sunscreen in the drips of perspiration, or does your sunscreen stay put once you rub it in?
• How fair and sensitive is your skin to the sun?
• Are you a 'hat person' and have hats handy for times you end up outdoors in the sun unexpectedly?

The easiest way to reapply zinc oxide sunscreen if you wear makeup is with a SPF 30+ powder sunscreen. 

You can dust a sunscreen powder on top of your 'real' sunscreen throughout the day. But, know that it is impossible to correctly dose sunscreen powder so don't depend on it for UV protection during intense UV exposure. Also, don't use it in place of a regular sunscreen. 

The bottom line about reapplying zinc oxide sunscreen:

Chuck, you have asked an excellent question. Your skin will tell you if you need to "up" your protection. We just don’t want to learn that lesson the really hard way with a burn or by getting a skin cancer. I tell my patients to watch carefully because a subtle tan is telling them to increase what they are doing for sun protection. 

Warmly,

Cynthia Bailey, MD, Dermatologist

Disclaimer: Please realize that availing yourself of the opportunity to submit and receive answers to your questions from Dr. Bailey does not confer a doctor/patient relationship with Dr. Bailey. The information provided by Dr. Bailey is general health information inspired by your question. It should not be a substitute for obtaining medical advice from your physician and is not intended to diagnose or treat any specific medical problem (and is not an extension of the care Dr. Bailey has provided in her office for existing patients of her practice). Never ignore your own doctor’s advice because of something you read here; this information is for general informational purpose only. This post is adapted from an excellent comment that Chuck sent to me in a blog post. I wanted to be certain everyone had a chance to see it because I know that many people share this question.