Differences between Chemical and Physical filters in sunscreens

Updated july 2025

Chemical and physical filters are the two main groups of sunscreens that protect us from the harmful effects of UVA and UVB rays. Sunlight can have positive effects, such as improving our mood, but excessive exposure can lead to skin problems such as pigment spots, wrinkles and even skin cancer. UVB rays vary in intensity depending on the season, location and time of day, while UVA rays are constantly present at all hours of the day and can even penetrate clouds and glass.

What are the effects of too much UVA and UVB rays on the skin?

1. UVA rays: Aging

UVA rays are present year-round, even on cloudy days and in winter. These rays penetrate deep into the skin and contribute to skin aging and silent inflammation, regardless of the season.

• Effects on the skin:
  • Aging: UVA rays penetrate deep into the skin and are responsible for premature aging such as wrinkles and sagging skin.
  • Pigmentation: Long-term exposure to UVA can lead to visible changes in skin pigmentation, such as sun spots.
• Protection:
  • Make sure you wear a broad spectrum sunscreen that blocks both UVA and UVB rays.
  • Wear protective clothing and seek shade during peak sunlight hours.

2. UVB rays: Skin burn

UVB radiation is seasonal and much stronger in spring and summer, especially around midday. It reaches the skin less in winter and on cloudy days.

• Effects on the skin:
  • Burn: UVB rays are the primary cause of sunburn, which makes the skin red and sometimes painful.
• Protection:
  • Apply a water-resistant sunscreen with a high SPF every two hours, especially during prolonged sun exposure.
  • Limit sun exposure between 10 a.m. and 4 p.m., when UVB rays are most intense.

Cancer risk

Both UVA and UVB: These rays contribute to the risk of skin cancer. UVB causes direct damage to the DNA of skin cells, while UVA contributes by forming free radicals that cause indirect damage and penetrate deep into the skin.

Differences between chemical and physical filters

Chemical filters

Chemical filters, consisting of organic compounds such as avobenzone, oxybenzone and octinoxate, work by absorbing UV radiation and converting it into harmless heat through a chemical process. The chemical compounds in sunscreens can absorb the sun’s UV rays. These compounds contain special molecules that have something we call pi electrons. Pi electrons can easily absorb energy, making them perfect for capturing UV light, which has a lot of energy.

Imagine these molecules as small, energy-absorbing bouncy castles. When UV light (which consists of tiny energy particles or photons) hits these inflatables, they absorb the energy of the photons. This causes the molecules to jump from a quiet state (the ground state) to a more energetic state (the excited state).

Now, molecules can’t remain energetic for long; they don’t like being so active. So, after a short time, they jump back to their original, calm state. When they do this, they release the absorbed energy, but now in the form of heat. This process helps convert the harmful UV rays into something less harmful, like heat, which helps protect the skin from sunburn and other sun damage.

Chemical filters, in other words.
Imagine a black car parked in the sun. The black on the car can absorb a lot of sunlight. After a while in the sun, the car feels very hot to the touch. This is because the car has absorbed the sunlight’s energy and is now radiating it as heat. In the case of sunscreen, the molecules in the cream absorb UV light in a similar way and convert it into heat, which is much safer for your skin.

While effective in providing UV protection, chemical filters can sometimes cause skin irritation or allergic reactions due to their penetration into the skin. This risk is increased in people with sensitive skin. Furthermore, some of these chemicals, such as oxybenzone, can have hormone-disrupting effects and have been found to be harmful to the marine environment, where they contribute to coral reef bleaching by disrupting the development of coral larvae. Fortunately, new chemical filters are in the works.

In addition, chemical filters usually require a processing time of about 15 to 30 minutes before they begin to work effectively. This is because they must first be absorbed by the skin to effectively absorb and convert UV radiation.

Physical (mineral) filters

On the other hand, physical, also known as mineral, filters such as titanium dioxide and zinc oxide provide UV protection by physically acting as a barrier on the skin, reflecting and scattering UV rays. Inorganic compounds, such as titanium dioxide and zinc oxide, are commonly used in sunscreens. These compounds work by blocking UV radiation in two ways: they absorb the radiation and they also reflect it. This happens because of something we call ‘electron-hole pairs’. Let’s simplify that a little.

Imagine that UV radiation consists of tiny energy particles. When these particles hit the inorganic compounds in the sunscreen, tiny holes and electrons (negatively charged particles) are created in the compound material. These holes and electrons together form pairs. These pairs help convert the energy of the UV light into another form of energy, such as heat, just as the chemical filters do.

The big difference between inorganic and chemical filters is how they interact with your skin. Inorganic compounds remain on the surface of the skin and do not penetrate the skin. This means they are less likely to cause irritation, making them a better choice for people with sensitive skin or certain skin conditions such as rosacea or eczema. Because they stay on the skin, they also help reflect UV rays, meaning they give the skin an extra layer of protection against sunburn and skin damage.

Mineral (physical) filters, in other words.
Think of sunscreen with these inorganic compounds as mirrored sunglasses. Just as sunglasses reflect light and protect your eyes, these compounds in sunscreen reflect UV rays away from your skin and also absorb some of the light, protecting your skin from the sun’s harmful effects.

Titanium dioxide is very effective against UVB radiation, while zinc oxide provides broad spectrum protection against UVA and, to a lesser extent, UVB rays. Both are photostable, meaning their chemical structure and protective properties do not break down in sunlight. Physical filters are also more environmentally friendly; they are not associated with harmful effects on the marine environment and are generally better tolerated by the skin.

Although physical filters can sometimes leave a white haze, recent developments in nanotechnology have minimized this effect without significant safety risks. Nano particles are so small that they cannot penetrate the skin, which is supported by recent research as safe.

New is iron oxide, protection against visible blue light.

Ironroxide is a relatively new ingredient in the world of sunscreens, and it serves as a physical filter, offering protection against visible blue light, also known as high-energy visible light (HEV light). This type of light is part of the spectrum we can see with the naked eye and comes from both the sun and digital screens such as smartphones, tablets, and computers.

How does iron oxide work as a physical filter?

Iron oxide works by physically blocking or reflecting visible light, similar to how titanium dioxide and zinc oxide block UV rays. It acts as a shield that lies on the skin, where it reflects and absorbs the light rays that can cause damage, such as the blue light rays. This is especially useful because blue light can penetrate deep into the skin and potentially cause damage such as skin aging and circadian rhythm disruption.

Benefits of iron oxide in sunscreens:

• Blue Light Protection: Iron oxide helps protect skin from blue light exposure, which has been linked to skin aging and may contribute to pigmentation conditions such as melasma, or dark spots.
• Safe for sensitive skin: Like other physical filters, iron oxide is not absorbed by the skin, making it less likely to cause irritation. This makes it suitable for people with sensitive skin or those prone to skin reactions.
• Instantly effective: Physical filters like iron oxide work immediately after application. There’s no waiting period required, unlike with chemical filters, which must first be absorbed before they become effective.

Iron oxide in other words. Think of iron oxide in your sunscreen as a small, invisible umbrella you spread over your skin. This umbrella not only blocks the sun’s UV rays but also the blue light from your computer or phone screen, protecting your skin from the different types of light you encounter daily. This makes iron oxide an excellent addition to sunscreens, especially for those who spend a lot of time in front of screens or outdoors.

The choice between chemical and physical filters depends on several factors, including personal skin sensitivity, environmental awareness, and specific skin needs. Physical filters are often recommended for their softness and stability, while chemical filters may be chosen for their lighter texture and stronger UV absorbing properties.

More about HEV protection with Ironoxide

What is SPF (Sun Protection Factor) on the packaging?

SPF indicates how many times longer someone can stay in the sun without burning when using sunscreen compared to not using sunscreen. If you don’t burn after 10 minutes of unprotected sunlight and you use a sunscreen with SPF 10, you can stay in the sun for 100 minutes without burning.

Sunscreens have different values. The values refer to the level of UVB protection (SPF), but say nothing about UVA or visible light protection.

So check your day cream with SPF to see if it also has UVA protection, because that is not always the case

Live consciously

Disturbing news and things you don’t think about when you’re sunbathing on the beach are the effects of sunscreens on marine life. It is estimated that 25-60 million bottles of sunscreen end up in the sea each year, either directly or through showering. After 20 minutes of swimming, 25% of the applied sunscreen ends up in the sea. Chemicals in sunscreen impact the DNA of coral and the ‘coral bleaching’ effect is enormous. Australians call the affected coral reef: Reef zombies. Coral, in turn, provides accommodation for 25% of all marine life in the ocean.

Mineral sunscreens have no environmental impact. Read more about this: Coral reefs

Sunscreen safe for marine life and coral: Sunscreenbulletin

Iconic Elements has deliberately chosen tinted mineral non-nano filters, titanium dioxide, zinc oxide, and iron oxide because they effectively block both UVA and UVB rays, as well as visible blue light, and are safe for people with sensitive skin, children, and pregnant women. Independently laboratory tested and passed the test. Effective immediately after application.

A Daycream with natural UVA filter protects the skin daily from the constant presence of UVA rays, which helps slow premature aging and collagen breakdown. Suitable for normal and dry skin. A UVA Defense Serum offers extra concentrated protection and can complement the daily cream, especially for prolonged daylight exposure or for skin prone to pigment shifts. Suitable for normal and sensitive skin.