After having three major sunburns in young age, I don’t want to go through the “peeling” stage again. The first sunburn happened in a dazzling sunny school sport day, second one happened in a cloudy day for beach activities, and the last one was shaded by umbrella, watching a F1 race in the scorching hot weather (only uncovered part had been “baked”). Unfortunately, sunscreen is an alien word to me at that time. In fact, since my freckles developed in 11 years-old, I learnt from my brother’s encyclopedia that avoiding direct sunlight is crucial but due to young brigade’s activities, that wasn’t really practical but I’ll seek shade whenever I can. At 20s, I learnt from Olay TV ads that we need some SPF everyday (no surprise I loyally adopted their SPF Moisturizer for many years then) but sunscreen still a strong chemical ointment for me (in fact they are) that only needed for hiking and water-sports. After age 30, only I learnt about photo-aging, started wearing sunscreen then.
When all beauty and medical experts told you that sun protection is a must for skin health, prevent photo-aging and skin darkening, I just have to agree by raising both my hands and legs. Comments by few readers of Beautyknot had prompted me to write this article and I want to delicate this post to those who are quite new to sunscreen but wanted to be little more sun-smart. My fundamental concept, as well as the gathering of following information were indicated as link from various sources.
UV (Ultraviolet) contains UVB (280~320nm), UVA-2 (320~360nm) and UVA-1 (360~400nm), together with UVC (100-280nm). UVC is the most dangerous but they are blocked out by the ozone layer, so they don’t reach the earth’s surface. The longer the UV wavelength, the greater ability to cause skin darkening and damaging. UVB induces sunburn, skin cancer, skin reddening and pain, while UVAs are responsible for wrinkling, pigmentation, loss of skin firmness and may be related to skin cancer with UVB.
Free-Radicals are atoms or a group of atoms with an odd number of electrons and can be formed when oxygen interacts with certain molecules. Once formed, it can start a chain of reaction like attack DNA or cell membrane, deplete collagen, causing skin lose its firmness and elasticity, slow down the cellular turnover…etc. Besides UV rays, other sources of free-radical included radiation, pollution, smoking, medication, stress, over exercising, deep-fried food…etc. Antioxidants can neutralize and stabilize free-radical.
Sunscreen (or sunblock) contains ingredients that provide at least certain degree of protection from sunburn and other damaging effects of the sun’s UV rays.
SPF (Sun Protection Factor) is measure of the time it takes the skin to burn. Depends on skin color, the fairer skin gets sunburn easier.
PA is rating system of UVA protection. The more plus sign, the higher protection against UVAs.
PPD (Persistent Pigment Darkening) is method of measuring UVA protection. The higher rating gives higher protection against UVAs.
UV index is an international standard to measure of how strong the UV rays from the sun at a particular place on a particular day.
Generally two major types of sunscreen, either chemical or mineral. However, certain chemical sunscreen, such as Tinosorb M acts like both chemical and mineral sunscreens.
- absorbs and disperse the UV rays
- examples of chemical sunscreens: Polysilicone-15, Tinosorb, Mexoryl, Avobenzone, Benzophenone, Dioxybenzone, Octyl Methoxycinnamate, Isopropylbenzyl Salicylate, …etc
- normally leaves no or minimum white residue
Mineral sunscreens (a.k.a Physical-blocker)
- reflect and scatter the UV rays
- normally leaves white residue (those in nano form render sunscreens transparent instead of pasty white)
- can be drying for drier skin condition
- safer and non-irritating to sensitive skin.
- mineral sunscreens: Titanium Dioxide and Zinc Oxide
Assuming your unprotected skin takes 20 minutes to get sunburn when being in the sun (fair skin has less tolerance to sun compare to tan skin) and you wear sufficient amount of sunscreen SPF30.
Then the calculation is SPF30 x 20 minutes = 600 minutes = 10 hours. That means, theoretically you can withstand 10 hours in the sun without getting sunburn. In other word, the higher rating of SPF, PA or PPD gives marginal better protection.
PA and PPD Conversion
I captured this picture from one of the beauty book, and I guess the conversion convinced some people turn to European sunscreens that usually have PPD10~35 for better UVA protection.
No sunscreens block 100% UV rays. Hence, try to minimize direct sun exposure between 10am-4pm in a sunny day, stay under shade or wearing umbrella/cap/wide-brimmed hat/sunglasses when necessary. For information, white cotton T-shirt gives SPF5, wet white cotton T-shirt gives SPF3, i.e. wet clothing is less protective than dry clothing. The tighter fabrics weave, the better it blocks UV rays.
Wear sunscreen appropriately, such as…
- wear at least SPF30 for active outdoor activities
- remove sunscreen thoroughly at the end of the day
- use gentle or mineral sunscreen for baby and kid
- wear sunscreen at night
- wear low SPF for insolation
- use non-water-resistant sunscreen for water-sport
You may also note that not all days/locations are created equal, you can find out about UV index at a given time/location in your area. However, the UV index is more useful in assessing the risk of sunburn (UVB) and tends to underestimate UVA exposure. Hence, as far as photo-aging concern, sun protection should be taken seriously even low values of the UV index.
Without applying sufficient amount, half amount of necessary sunscreen of SPF 50 can turn out to be SPF7.1. That’s very important to apply enough amount of sunscreen besides reinforce high SPF, PA and PPD.
Guideline from FDA, appropriate amount for desired protection is 2mg/cm2 (EU: 1.5mg/cm2), translates into 1/4-1/3 teaspoon for an average adult face. To be precisely, the 2mg/cm2 is for “average” adult build of height 5ft4in (163cm), and weight 150lb (68kg), with a 32 in (82cm) waist, that adult wearing a bathing suit covering the groin area should apply 29g (~1oz) evenly to the uncovered body area.
On the other hand, Australia standard is far stringent. For an adult, the recommended application is 5ml (approximately 1 teaspoon full) for each arm, leg, body front, body back and face (including neck and ears). That equates to a total of 35ml (approximately 7 teaspoons full) for a full body application.
The adequate amount should be estimated accordingly. For example, the estimated surface area for my face is roughly 516cm2. Based on the given formula, I need approximately 1.9g for face and neck. However, I normally take 1.5 months to finish a 30ml (1 fl.o.z) sunscreen, including occasionally reapply. Obviously I didn’t apply enough most of the time, but I didn’t expose to hours direct sunlight either.
Common practice is, apply sunscreen after skin care routine, however I read different opinion here that sunscreen should apply first, before skin care and makeup. Frankly, I never read any other experts mentioned about the efficacy of sunscreen can be interfered by next product, but I always read countless experts emphasize on penetration of harmful chemical sunscreens can risk our health and their say is strongly supported with convincing evidence. Studies show certain chemical sunscreens can trigger ROS when exposed to sunlight. Therefore, stick to those low absorption chemical sunscreen or safer formulation. Regardless chemical or mineral sunscreen, virtually none of them is safe if absorbed into skin.
Conversely, skin care is formulated to be more skin receptive (with all those penetration enhancers and solvents) in order to improve skin texture more aggressively, unless you’re ingredient specialist, else there are too many uncertainties to tell. For instance, that could be all good/bad ingredients are getting chance to be absorbed into skin with poor-formulated sunscreen. Or, wasting the high treatment potent ingredient of following product by applying sunscreen first if the sunscreen used will create a protective film on skin. Nevertheless, if the sunscreen is well-formulated and won’t penetrate into skin deep, then I can see the possibility to apply sunscreen first/alone (In fact, that’s what I did for body skin sometimes). Furthermore, we need antioxidants, soothing and moisturizing properties to assist in achieving beautiful healthy skin. You can either apply skin care for that purposes prior to applying sunscreen, or your sunscreen is already containing these helpful ingredients.
In short, skin care ingredients such as soothing, moisturizing and antioxidant that don’t necessary to be absorbed deeply into skin dermis are best choice to be used together/after chemical sunscreen because they can work out well in upper skin. Minimize risk of skin irritation by avoiding complicated high treatment chemical sunscreen such as anti-aging and whitening.
Certain chemical sunscreens pose higher risk to health than mineral sunscreens. For instance, Oxybenzone is high absorption through skin, high rates of allergic reactions, and growing concerns about hormone disruption. So, ensure the sunscreen is well-formulated to minimize the risk of penetration.
Nanotechnology of sunscreen ingredient is the prime concern. Studies show little to no zinc and titanium absorbs through the skin, and they provide relatively stable protection compared to the other sunscreens. However, zinc and titanium in spray or powder sunscreens aren’t recommended as inhalation of zinc and titanium particles is a concern that may have greater toxicity to skin and living environment. By convention, definition of nanotechnology included anything one or more external dimensions is in the size range 1 nm – 100 nm. EWG has advised the US Environmental Protection Agency and FDA to broaden its criteria to cover particles larger than 100 nanometers (nm) in at least one dimension because some larger particles may exhibit toxicity effects similar to smaller ones. (source)
From the above table, you will get a clear overview how capable of those sunscreens filter UV wavelength. Unfortunately, I couldn’t find much detailed information about Mexoryl and Tinosorb.
From the above table, Avobenzone (320~400nm) gives full spectrum to UVAs, but it’s not photo-stable that break down into unknown chemicals when exposed to sunlight, especially in the presence of another active ingredient- Octinoxate, thus lose its sun protection potency and required frequent re-apply to ensure the protection. Most sunscreens are using Octocrylene to stabilize Avobenzone, but experts would still advise you to re-apply every two hours for continuous UV protection. In addition, uncoated mineral powders can degrade the efficacy of Avobenzone, so avoid using these ingredients together.
Mexoryl SX (Ecamsule or Terephthalylidene Dicamphor Sulfonic Acid) usually to be used together with Mexoryl XL (Drometrizole Trisiloxane) because they show synergistic effect in protection. Mexoryl is low skin penetration thus relatively safe. Mexoryl XL has peak absorption at 303nm and 344nm. Currently only Mexoryl SX is approved by FDA in US, however two hours of sunlight can degrade Mexoryl SX as much as 40% of this active ingredient. In most case, Mexoryl SX is formulated together with other sunscreens to increase its broad-spectrum (UVA and UVB) protection. (source)
Tinosorb on the other hand is photo-stable (remains stable in sunlight) and provides broad-spectrum protection from what I read here and here. Tinosorb also has low skin penetration. Tinosorb S (Bemotrizinol) is oil-soluble while Tinosorb M (Bisoctrizole, both chemical and mineral agents) is water-soluble and Tinosorb M provides about 280-400 nm (both UVB and UVA) protection range, peak protection at 303 nm and 358nm. However, it’s produced via nanotechnology though it rated low-risk compared to other chemical sunscreens. By absorbing, reflecting and scattering the sun’s UV rays, Tinosorb M provides reliable broad spectrum coverage of UV rays.
Sunscreens with Mexoryl XL and Tinosorb currently are available in EU, Australia, Canada, Japan and many other countries but not yet approved in U.S (source). (Note: Sunscreen containing Mexoryl SX was given approval in US in 2006 under New Drug Application but not Mexoryl SX itself. source)
Efficacy of each sunscreen is important, but overall rating of the sunscreen formulation could be much more important. Many of us may not fully understand how to choose a well-formulated sunscreen on the market. Professional’s choice may be a helpful guideline.
Criteria of a good sunscreen must be:
- broad-spectrum ( provides protection against both UVA and UVB rays)
- high stability of active ingredients (remain stable in the sun, i.e. photo-stable)
- safe (low skin absorption)
- water-resistant (still provides marginal protection while in the water)
- sweat-resistant (still provides marginal protection while sweating)
- including antioxidants, moisturizing and soothing ingredients (optional but recommended, can be achieved by skin care routine prior sunscreen application to against free-radicals, reduce irritation and inflammatory, etc)
Besides, if you’re wearing moisturizer SPF25, sunscreen SPF30, makeup foundation SPF 15, the total sun protection you would get is the highest one, that means SPF30 in total, not the sum up total SPF70.
If the sunscreen consistency is heavy, sticky, oily, uncomfortable wearing and intolerable scented, eventhough it’s well-formulated and provides effective sun protection, I doubt whether the sunscreen is sellable. Not to mention potentially comedogenic and acnegenic issues for certain skin types and in particular weather. Therefore, the sunscreen consistency should agree with your skin and meet your requirements, at least you’re more willing to daub on adequate amount on skin. Follow the product direction for face or body, or both.
In order to achieve desired sun protection, apply adequate amount is a must. Instead of applying the generous amount at one go which probably hard to blend evenly or being greasy or leaves heavy white tint, you can separate the amount into two or few applications. Wait the previous protective film formed, then apply another layer. Or, slowly build up if the sunscreen texture is lightweight enough.
If you are heading for outdoor activities such as swimming, do use very water and sweat resistant sunscreen and apply 15-30 minutes before sun exposure. Re-apply liberally every 2 hours for continuous protection. A water-resistant sunscreen can maintain its SPF up to 40 minutes when being submerged in water.
If you are staying indoor with minimum casual sun exposure, apply 15-30 minutes before sun exposure for better adherence, then re-apply only if the sunscreen effect has been wore off. That could be:
- when you wiping/blotting/rubbing the skin (eg: excess sebum on face, tearing or sweating).
- sunscreen ingredients such as Avobenzone and Mexoryl SX that are unstable when exposed to sunlight.
However, bare in mind that UVA can pass through 5cm glass and it can be reflected from the majority of common surfaces (such as wall), so even you stay indoor, clear glass allows up to 75% of UVA to pass. Tinted and reflective glass absorbs more of the UVA but still allows about 25-50% to pass. When outside, UV rays can be refracted via clouds, snow, beach sand or water, you might need to take higher measure of UV protection accordingly. Read more here and here.
Vitamin D deficiency is serious health concern. Approximate 90% of vitamin D is made naturally through sun exposure to the unprotected skin. Experts advised 15 minutes (light-skin) daily sun exposure without sun protection in sunny day (early morning or late afternoon) is sufficient for an adult. Darker skin may require up to 40 minutes.
Cosmetic With Sunscreen
Certain cosmetics are also containing sunscreen but the sun protection measurement (SPF, PA, PPD) isn’t listed on packaging/product label. This type of product is categorized as cosmetic by FDA, not sunscreen. Hence, they’re not providing broad-spectrum protection against UV rays.
My Final thought:
Normally, the efficacy of sunscreen is prime concern to many of us, leading the higher SPF and PPD sunscreen is more sellable or product with sunscreen is preferred. Most common sunscreens I saw on the current Asia market are mixture of both chemical and mineral. As far as sensitive skin concern, safety should be the most crucial point.
Last but not least, this is most complicated, dizziest, longest post that I ever wrote on this blog. Honestly I may not knowledgeable enough to fully interpret all the information I’ve read and I certainly don’t want to mislead anyone here. Therefore, if you have different opinions with verifiable source provided, or should you want to contribute additional info, welcome to leave a comment. Thank you.