Sunscreen Myths and Facts - Top 15 Questions
Does sunscreen go bad? What does SPF even mean? What’s the deal with sun-protective clothing? How much sunscreen should we put on our face and body? Is sunscreen even safe? We’ve vetted your top sunscreen questions against the research of medical professionals to ensure you’re protected and armed with the truth about sun safety.
Let Paula’s Choice experts help you bust those myths and boost your understanding of facts about sunscreen. Read on to find out more.
Does Sunscreen Expire?
Sunscreen does indeed expire. To ensure safety and efficacy, the United States Food and Drug Administration (USFDA) requires sunscreen products to list an expiration date, usually found on the packaging or printed along the crimp portion of tube-packaged SPF products.
However, there is one exception to this rule: If the manufacturer has proven that their sunscreen will remain stable for at least three years via stability testing, the product doesn’t have to be stamped with an expiration date. In that case, the FDA warns that the product “should be considered expired three years after purchase”. We’d even go one step further to say that once you open the product, it’s a safer idea to use it up before the PAO (period after opening) date, which is usually 12 months for cream/lotion sunscreens.
A helpful tip is to practice testing expired products on a small part of your body before using them elsewhere. This practice ensures that you do not have any adverse reactions to the product.
Note: Sunscreens sold outside of Singapore may be subject to different expiration policies, so it is essential to read and understand the label to ensure you’re getting reliable sun protection.
Can You Use Expired Sunscreen?
Expired sunscreen should not be relied on to protect your skin, as there is no assurance that the use of these sunscreens will be fully effective. While you might still get some protection after you put the product on, there’s no way to know exactly how much—in other words, using expired sunscreen leaves you vulnerable to sunburn. Insufficient sunscreen on your face and body can lead to sunburnt skin and UV damage that harms the skin in the long run, accelerating signs of aging. Most importantly, insufficient sun protection can increase the risk of skin cancer, so it is always better to err on the side of caution and purchase a new sunscreen.
Does Sunscreen Go Bad after Sitting in the Sun?
Leaving your sunscreen in the direct sun for an extended period can harm the formula’s stability. To keep your SPF in tip-top condition, especially on beach days, the FDA recommends providing protection for your sunscreen by wrapping it in a towel or storing it in the shade or a cooler.
Does Sunscreen Prevent Tanning?
A well-formulated sunscreen will prevent tanning or the deepening of skin’s colour as it works to shield skin from the harmful rays responsible for triggering that response. However, research shows that user error in under-applying sunscreen is still prevalent both in the United States and many other countries, which could mean you may still see a tanning effect or sunburn on the skin even after applying SPF. One of the biggest mistakes most people make is not using or reapplying sunscreen on their face and body liberally enough to achieve adequate protection.
It's also important to point out that sunscreen does provide 100% protection from UVA and UVB rays. This gives you even more reason to couple sunscreen use with other sun-smart behaviours, such as seeking shade when possible and wearing sun-protective clothing, especially on days when you’ll be exposed to the sun for more extended periods. Speaking of which…
Do you need Sunscreen if you have Sun Protection Clothing?
Sun protection clothing from reputable brands will shield your body against UVA and UVB rays, so no sunscreen is necessary underneath the clothed area. However, any areas of skin that are left exposed to the sun still need sunscreen. Some oft-overlooked areas while applying sunscreen include the tips of your ears, sides of your face and ankles. Like sunscreen, you want to look for clothing rated with a UPF (ultraviolet protection factor) of 30 or higher to prevent overexposure to the sun and sunburn.
What is UPF and how does it Differ from SPF?
UPF is the rating system used to identify the level of sun protection provided against UVA and UVB rays by specific clothing or headgear for your body and face. This differs from a sunscreen’s SPF rating, which only signifies effectiveness against UVB rays. To ensure UVA protection, your sunscreen must be labelled as “broad spectrum”, indicating the presence of sunscreen ingredients that protect against UVA wavelengths.
Wait, SPF doesn’t measure UVA rays—what’s up with that?! Let’s delve into how sunscreens work in a bit more detail…
How does Sunscreen Work?
Sunscreen actives work in the skin's uppermost layers to absorb and, to a lesser extent, deflect and scatter the sun’s harmful rays. Think of them as shields for your skin—while not wholly failproof, they do an excellent job of hindering damage to the skin from the sun to the extent possible.
As mentioned earlier, SPF is a rating system that measures how much UVB protection a product delivers when applied evenly and liberally. UVB rays are the rays that trigger sunburn and other visible changes to the skin’s surface, including discolourations. UVB radiation also plays a role in skin cancers. Its intensity wavers depending on your geographic location, altitude, time of day, and cloud cover level (but make no mistake, clouds still let harmful UV light through).
UVA rays are an even more significant threat because a much larger percentage of them reach the earth’s surface and our skin. UVA rays are present at the same intensity all day long. They penetrate further into the skin than UVB rays, steadily destroying key substances that give skin a youthful, healthy appearance. Moreover, UVA rays are a significant contributor to every type of skin cancer. Remember, your sunscreen must be labelled “broad spectrum” to ensure it protects against UVA rays…the SPF number itself doesn’t tell you that.
Note: Sunscreens in Asia and other parts of the world are labelled with a PA+ rating and a UVA protection measurement. However, this rating is not available for US-based sunscreens yet.
How Long does Sunscreen Last?
Once you’ve applied your sunscreen, how long it will last (protect your skin) depends on several factors. The general recommendation is to reapply every two hours for your skin to receive optimal protection.
In the past, it was thought that if you knew how long it takes your skin to turn pink or begin to darken when exposed to the sun, then you could take that amount of time in minutes and multiply it by the SPF number on the bottle to determine how long it will protect your skin. However, SPF ratings aren’t just about time. They’re also about the intensity of UVB based on your location, amount of cloud cover, latitude, season, and proximity to reflective surfaces like water, snow, and sand.
Additionally, you must consider whether you’re sweating, swimming, or doing anything else that might dilute or rub off your sunscreen.
Complicated, right? That’s why the two-hour reapplication rule tends to stick, even though it oversimplifies things.
However, the two-hour reapplication rule isn't necessary if you’re indoors for almost the entire day without contact with the sun through any windows. This is because UV rays aren’t actively breaking down the sunscreen applied to your face or body, and you’re not perspiring heavily; therefore, it is still protective.
Is SPF 30 Enough?
Medical organisations worldwide recommend broad-spectrum SPF 30 sunscreen or greater for daily use. While that may be enough for most people in their daily lives, whether SPF 30 will be enough for you depends on how much exposure you’re likely to get. Obviously, hanging outside at the beach all day will impact your skin differently than spending the entire day indoors at the office. For days that you know your skin and body will be more exposed to the sun, reaching for a higher SPF of 50 isn’t a bad idea. Don't forget a broad-brimmed hat and sunglasses.
When was Sunscreen Invented?
While previous civilisations used various measures to limit sun exposure, research points to 1928 as the first documented use of a sunscreen emulsion in the United States, which used UVB filters to protect against sunburn . However, there’s a bit of debate among historians about who actually invented the first commercialised sunscreen. That aside, we do know the development of specifications for sun protection factors didn’t occur until 1974, and in 1980 the first documented sunscreen with UVA filters was released. In the decades since then, sunscreen formulations have improved by leaps and bounds in terms of aesthetics, efficacy, and options for all skin types and skin tones.
Does Sunscreen Block Vitamin D?
While it’s a fact that sunscreen inhibits exposure to UVB rays that trigger vitamin D production in the skin, research shows foregoing sunscreen in order to get more vitamin D is not the answer. Sunscreen’s effect on vitamin D levels is considered minimal for most people, and ironically, skipping sunscreen and getting a tan is a harmful myth about vitamin D in its own way. What we know to be unequivocally true is that exposing your skin to harmful UV rays has serious repercussions.
If you’re concerned about vitamin D deficiency, there are far more effective ways to get this nutrient. According to board-certified dermatologist Dr Joyce Park, “Vitamin D is also easily obtained through your diet, through fortified dairy products, egg yolks, cheese, seafood, and more.”
When can a Baby use Sunscreen?
For babies under six months, the American Academy of Pediatrics recommends sun-protective clothing and seeking shade when possible. When sun avoidance isn’t an option, using mineral-based (zinc oxide or titanium dioxide) sunscreen on exposed areas of skin, such as the face and hands, is recommended. For babies six months and older, regular sunscreen application is advised. As always, consult your child’s paediatrician and follow their advice.
“Never spray sunscreen onto your child’s face directly due to inhalation risk; instead, spray the sunscreen onto your hands and pat onto the child’s face,” cautions Dr Park.
Can Sunscreen cause Acne?
Sunscreen in and of itself does not cause acne. However, if the formula you use on your face or body has a thick, heavy, pore-clogging consistency, there’s a chance you could break out from it if you do not cleanse thoroughly.
For acne-prone skin, lighter weight, non-greasy, fluid sunscreen formulas like the CLEAR Ultra-Light Daily Hydrating Fluid SPF 30+ are a better sunscreen option. At night, remove traces of the sunscreen with a gentle yet thorough cleanser such as the CLEAR Pore Normalizing Cleanser.
Is Sunscreen Safe?
While the safety of sunscreen has been called into question by media headlines in recent years, the FDA and the American Academy of Dermatology still strongly agree that wearing sunscreen is safe and plays a crucial role in protecting your skin. Scientific studies also support this, and most notably, research shows sunscreen use reduces the risk of skin cancer and sunburn.
Some of the concern around sunscreen use was heightened in September of 2021 when the FDA announced that they would be taking steps “aimed at improving quality, safety and efficacy of sunscreens,” including analysing more data on certain UV filters. It’s important to point out that this doesn’t mean those ingredients are unsafe, nor has the FDA issued a warning to stop using them or advised formulators to avoid them.
If you have additional questions about the safety of your sunscreen, a board-certified dermatologist can help.
What Ingredients to Avoid in Sunscreen?
While there’s no reason to avoid approved sunscreen filters, what you should avoid are known irritants that commonly show up in sunscreen products. High amounts of alcohol (denatured or SD) and fragrance (synthetic or natural) are two of the top offenders in sunscreen formulations. These are known risks to the skin for their sensitising and barrier-weakening effects.
“If you have especially sensitive skin, you may want to opt for mineral-based sunscreens (zinc or titanium-based), as those have been shown to be less irritating to the skin than chemical filters,” adds Dr Park.
Learn more skincare and sun care tips.
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References for this Information
- FDA.gov, September 2025, ePublication
- Journal of the European Academy of Dermatology and Venereology, November 2019, pages 1,112–1,117
- Photodermatology, Photoimmunology, and Photomedicine, January 2022, pages 1-11
- Australian and New Zealand Journal of Public Health, 2019, ePublication
- Saudi Pharmaceutical Journal, November 2019, pages 1,009-1,018
- Journal of Cosmetic Dermatology, April 2021, pages 1,044-1,049
- Journal of Korean Medical Science, January 2020, https://doi.org/10.3346/jkms.2020.35.e50
- American Academy of Pediatrics, August 2024, ePublication
- American Academy of Dermatology Association, April 2022, ePublication
- Cosmetics, July 2019, https://doi.org/10.3390/cosmetics6030042
- Forbes, May 2024, ePublication
- Skin Cancer Foundation, July 2021, ePublication
