What are sunscreen filters?

Sunscreen filters are active ingredients used in cosmetic products to protect the skin from the harmful effects of ultraviolet (UV) radiation. They work by minimizing the damage caused by UVA rays (responsible for skin aging) and UVB rays (which cause sunburn), thereby reducing the risk of photoaging, hyperpigmentation, and skin cancer. In addition to UV radiation, there are other types of solar radiation that can also affect skin health.

Types of Solar Radiation and Their Effects on the Skin

Ultraviolet (UV) Radiation

UV radiation is the most relevant for the skin and includes UVA, UVB, and UVC rays:
  • UVA rays penetrate the deepest into the skin, contributing to photoaging, oxidative damage, pigmentation, and skin cancer.
  • UVB rays act more superficially (on the epidermis), causing sunburn (erythema), DNA damage, redness, and also contribute to skin cancer.
  • UVC rays are absorbed by the ozone layer and do not reach the Earth's surface.

Visible Radiation (VIS)

This is the portion of the electromagnetic spectrum visible to the human eye. It represents only a small fraction of solar radiation. While it doesn’t cause burns like UV rays, visible light, especially blue light (HEV), may contribute to photoaging and skin pigmentation.

Infrared Radiation (IR)

Infrared is an invisible light located just beyond red in the electromagnetic spectrum. It doesn’t burn the skin but produces heat and penetrates deep into the dermis. It generates free radicals responsible for oxidative stress, which contributes to premature skin aging.

When formulating sunscreens, it is important to consider not only UV protection but also ingredients that help counteract the effects of visible and infrared radiation.

Types of Sunscreen Filters: Chemical, Physical, and Biological

Chemical Filters (Organic)


These filters absorb UV radiation and transform it into harmless heat. They are organic compounds that act via photochemical mechanisms.
  • Common examples:
Butyl Methoxydibenzoylmethane: UVA protection
Ethylhexyl Methoxycinnamate: UVB protection
Octocrylene
  • Advantages:
Lightweight, cosmetically pleasant textures
High efficacy at low concentrations
  • Disadvantages:
Some may cause irritation or allergic reactions
Can degrade with sunlight unless stabilized
Some are restricted in certain regions (e.g., benzophenones, oxybenzone)

Physical (Mineral/Inorganic) Filters


These reflect and scatter UV radiation. Common physical filters include:
  • Zinc Oxide (ZnO): Broad-spectrum protection (UVA + UVB), highly tolerated (ideal for sensitive skin and babies), stable under light. May leave a white cast.
  • Titanium Dioxide (TiO₂): Mainly protects from UVB and some UVA (less than ZnO). Better cosmetic appearance, but doesn’t fully cover the UVA range. Needs to be combined with other filters. Can also leave a white cast.
 Advantages: Stable under heat and light
Ideal for sensitive or atopic skin
Immediate protection after application
  • Disadvantages:
May leave a white residue (can be minimized with nano/micronized particles)
Harder to reach high SPF without combining with other filters

Biological Filters

Biological filters are antioxidant substances that prevent the formation of free radicals and support the skin’s immune system. Examples include:
  • Vitamin C
  • Vitamin E
  • Carotenoids
  • Green tea polyphenols
  • Flavonoids

What Is SPF (Sun Protection Factor)?

SPF is the number indicated on sunscreen packaging that estimates how much UVB radiation is required to cause sunburn (erythema) on protected skin compared to unprotected skin.

Theoretically, if a person burns after 40 minutes of sun exposure without protection, an SPF 30 would multiply that time by 30. But this is only a guideline — real-life effectiveness is affected by: Sweat, water, and environmental factors, amount of product applied, and Solar intensity

That’s why experts recommend reapplying sunscreen every 2 hours, even with high SPF.

UVB blocking percentages by SPF level:

SPF 15: blocks ~93% of UVB

SPF 30: blocks ~97%

SPF 50: blocks ~98%

How Is Sunscreen Efficacy Measured?

  • SPF (Sun Protection Factor): measures UVB protection
  • PA / UVA-PF: measures UVA protection
  • Broad spectrum: ensures the product protects from both UVA and UVB rays

Testing methods can be in vivo, in vitro, or mathematical models, depending on regulations (FDA, ISO, COLIPA, etc.).

What to Consider When Choosing Filters for Formulation

  • Product type: cream, gel, spray, makeup, stick, etc.
  • Target audience: babies, sensitive skin, oily skin, athletes, etc.
  • Regulatory requirements by market (EU, USA, Asia)
  • Stability and compatibility (pH, oxidation, fragrance, colorants)
  • Claims: reef-safe, natural, water-resistant, high SPF
  • Desired texture: physical filters may need special emulsifiers for better sensorial properties

Reef-Safe or Sustainable Sunscreens

More brands are seeking environmentally friendly sunscreens. Ingredients like oxybenzone or octinoxate are restricted in areas such as Hawaii due to their impact on coral reefs.

Common reef-safe filters:

Non-nano Zinc Oxide
Non-nano Titanium Dioxide
Encapsulated or micro-dispersed filters
 
If you're developing or reformulating a sunscreen, contact us for technical advice and up-to-date technical data sheets.