Sunscreen is now an essential part of daily skincare routine, regardless of the season or skin type. It protects against harmful UVA and UVB radiation, slows the aging process, and prevents skin discoloration. Despite this, many myths still surround sunscreens, from concerns about their absorption through the skin to their alleged impact on hormonal balance.
Do UV filters really penetrate the body? Is it safe to use sunscreen daily? And how can you distinguish an effective ingredient from a controversial one?
In this post, we examine the facts – analyzing the effects of sunscreens , their safety, the differences between chemical and mineral filters, and the latest recommendations from experts and the European Commission. If you want to make an informed choice about choosing a safe sunscreen and understand how SPF protection works, read on.
How do sunscreens work?
Sunscreens with SPF don't just protect against sunburn—they're also a cornerstone of anti-aging, skin cancer prevention, and discoloration reduction. Their primary purpose is to protect the skin from the harmful effects of ultraviolet radiation , specifically UVB and UVA . Depending on the type of filter used (chemical or mineral), the mechanism of this protection may technically differ, but the goal is the same: to protect skin cells from damage and premature aging .
What exactly is SPF?
SPF (Sun Protection Factor) is a rating that indicates how effectively a product protects the skin from UVB radiation , the type responsible for redness (sunburn). For example, a sunscreen with SPF 30 means that skin protected with it theoretically takes 30 times longer to turn red than unprotected skin. However, it's important to remember that SPF doesn't indicate protection from UVA radiation—that's handled by separate labels, such as UVA in a circle (compliant with EU requirements) or the PA+ scale used in Asia.
The difference between UVB and UVA radiation
- UVB (290–320 nm) is shortwave radiation responsible for sunburn and skin damage . Its effects are intense but limited primarily to the surface layers of the skin.
- UVA (320–400 nm) is long-wave radiation that penetrates deeper into the dermis , where it damages collagen, elastin, and cellular DNA. It is the main culprit in photoaging , pigmentation disorders, and oxidative stress.
A well-formulated sunscreen should protect against both UVB and UVA rays . Therefore, when choosing a cosmetic, it's worth paying attention not only to the SPF level but also to the full spectrum of protection declared by the manufacturer.
Types of UV filters – chemical vs. mineral
Sunscreens are divided into chemical (organic) and mineral (physical) types . They differ not only in their mechanism of action but also in their application properties, stability, and skin tolerance. In practice, many modern SPF cosmetics combine both types, creating so-called hybrid formulas that provide a broad spectrum of protection and comfort of use.
Chemical (organic) filters
Chemical filters work by absorbing UV radiation energy . When applied to the skin, they partially penetrate the stratum corneum and convert UV energy into harmless heat before it can damage cells.
The most commonly used include:
- Avobenzone (Butyl Methoxydibenzoylmethane) – effective UVA filter, but requires stabilization.
- Octocrylene – a stable UVB and partially UVA filter, often used as a booster for Avobenzone.
- Homosalate – a UVB filter, popular in the USA, less used in the EU due to concentration restrictions.
Advantages:
- High effectiveness at low concentrations,
- Good cosmetic properties (invisibility, no whitening),
- Possibility to combine multiple filters for full spectrum protection.
Defects:
- May cause allergic reactions and irritations (especially in sensitive skin),
- Some chemical filters may penetrate into the bloodstream – which is controversial (although penetration ≠ toxicity),
- They require stabilization and an appropriate support system.
Mineral (physical) filters
Mineral filters work by physically reflecting and dispersing UV radiation . They create a thin, protective layer on the skin's surface that reflects light like miniature mirrors.
The most commonly used are:
- Zinc Oxide – a broadband filter that protects against both UVA and UVB.
- Titanium Dioxide – effectively blocks UVB and short-wave UVA.
Advantages:
- Very good skin tolerance (suitable even for children and pregnant women),
- Low skin permeability – not absorbed into the body,
- They provide protection immediately after application (no need to "wait").
Defects:
- They may leave a white film on the skin , especially at higher concentrations and without the use of nanotechnology,
- Less resistant to sweat and abrasion – require reapplication,
- Sometimes more difficult to spread (thicker consistency).
Are sunscreens absorbed?
The question "Do sunscreens absorb?" has gained enormous popularity in recent years—primarily due to media reports, US FDA research, and consumer concerns about the potential health impact of UV filters. To answer this question honestly, it's worth distinguishing two completely different phenomena:
What does "absorption" mean? Skin vs. bloodstream
In the context of cosmetology, we talk about absorption in two ways:
- Absorption into the epidermis and dermis is a completely natural and desirable phenomenon. Many active ingredients (e.g., vitamin C, retinol, hyaluronic acid) work in this way.
- Absorption into the bloodstream (also known as systemic penetration) is the process by which active substances penetrate the skin layers into the general circulation. This possibility is controversial when it comes to chemical filters .
Cream absorption ≠ filter absorption
It's important not to confuse the absorption of a cosmetic product as a whole (i.e., the sensation of the cream "absorbing" into the skin) with the absorption of active ingredients at a biological level . A sunscreen may spread easily and disappear quickly from the skin's surface—but that doesn't mean its active ingredients automatically enter the bloodstream.
Most modern UV filters work in the upper layers of the epidermis , where they absorb or reflect solar radiation. This is where UV protection occurs— on or just below the skin's surface .
What the research says – FDA and in vivo testing
In 2019 , the FDA (U.S. Food and Drug Administration) published a groundbreaking study demonstrating that certain chemical sunscreens (including avobenzone, oxybenzone, octocrylene, and homosalate ) could be detected in blood after repeated sunscreen applications under test conditions. Concentrations exceeded accepted safety thresholds (0.5 ng/ml), above which further toxicological evaluation is recommended.
However, it is important that:
- it has not been shown that penetration itself means harmfulness ,
- the test conditions were very intense (e.g. application of 2 mg/cm² to the whole body, 4 times a day for 4 days),
- The FDA did not ban the use of these filters, but recommended further study.
Similar in vivo tests conducted in Europe and Asia do not confirm a clear health risk under conditions of everyday use.
It's worth knowing that the cream as a whole is absorbed into the epidermis, but most UV filters act on the surface . Some chemical filters can penetrate the bloodstream , but they haven't been shown to be harmful under typical use. Presence in the bloodstream ≠ toxicity – what matters is the dose, exposure time, and metabolism .
UV filters and safety – what does science say?
The safety of sunscreens is a topic regularly reviewed by the scientific community, regulatory bodies (such as the FDA, SCCS, EWG ), and manufacturers themselves. Contrary to popular concerns, the vast majority of sunscreens available on the market are safe when used as directed.
Research on the toxicity and metabolism of filters
Over the last 20 years, hundreds of toxicological and pharmacokinetic studies have been conducted, assessing, among others:
- skin permeability,
- accumulation in tissues,
- influence on hormones (estrogenic/androgenic effect),
- metabolism and excretion.
The results show that most chemical filters do not exhibit significant toxic effects at the doses used in cosmetics , and penetration into the body (if any) is usually minimal and reversible .
What did the FDA and EWG studies find?
- FDA : showed the presence of selected filters in the blood, but did not ban their use – it only recommended further long-term testing.
- EWG (Environmental Working Group) : an environmentally friendly organization, often critical of chemical filters, especially oxybenzone – it points out its potential hormonal effects in animals (but not confirmed in humans).
- The European Commission (SCCS) has only approved filters whose safety profile is known and considered acceptable .
Are UV filters carcinogenic?
There is no evidence that UV filters in cosmetics cause skin cancer. On the contrary, their use reduces the risk of squamous cell carcinoma and melanoma by protecting cell DNA from UV radiation damage.
Controversy regarding the potential carcinogenicity of some sunscreens (primarily oxybenzone) has been based on in vitro or animal studies, using doses many times higher than those used in cosmetics. These studies have not been confirmed in humans .
Risk-benefit analysis
From a dermatological and cosmetological perspective , the benefits of using UV filters far outweigh the potential risks . Regular use of sunscreen :
- protects the skin against photoaging and wrinkles,
- reduces the risk of discoloration and sun spots,
- protects against skin cancer.
Even if some filters penetrate the body, they:
- they do not accumulate,
- are quickly metabolized and excreted,
- do not show significant toxic effects in clinical trials.
Filters and penetration into blood and hormones – what do we really know?
More and more people are asking: do sunscreens penetrate the bloodstream and affect hormones? This topic has become especially popular following the publication of FDA studies and numerous articles on social media. While some reports may be alarming, it's worth examining the facts—separating them from media panic.
