viewBox="0 0 20 20" fill="none" width="20" height="20" aria-hidden="true"> UV Filter (Water-soluble)

BENZOPHENONE-4
Water-soluble Organic UV Filter (Benzophenone Derivative)

BENZOPHENONE-4 is produced synthetically by sulfonating benzophenone-3 (oxybenzone). Learn everything about its origin, effect, and the best application in your daily skincare routine here.

Also known as: Sulisobenzone, BP-4
Substance Class Water-soluble Organic UV Filter (Benzophenone Derivative)
INCI Name BENZOPHENONE-4
CAS Number 4065-45-6
Quality EU Cosmetics Regulation compliant

viewBox="0 0 24 24" fill="none" width="32" height="32" aria-hidden="true"> What is BENZOPHENONE-4?

Benzophenone-4 (also called sulisobenzone) is a synthetic UV filter that primarily absorbs UVB radiation and is used in cosmetic sun protection products. The special feature: as one of the few organic UV filters, it is water-soluble — made possible by a sulfonate group on the benzophenone backbone. This makes it ideal for light, non-greasy formulations such as gels, sprays, and aqueous lotions. Developed in the 1970s as an alternative to purely lipophilic UV filters, it enables more pleasant-to-wear sun protection products. In the EU, Benzophenone-4 is listed in Annex VI of the Cosmetics Regulation with a maximum concentration of 5%. The filter is increasingly being supplemented or replaced by newer, more photostable, and broad-spectrum UV filters, but remains a proven component in modern sun protection formulations.

viewBox="0 0 24 24" fill="none" width="32" height="32" aria-hidden="true"> Where does BENZOPHENONE-4 come from?

It is produced synthetically through the sulfonation of benzophenone-3 (oxybenzone). The sulfonate group makes the filter water-soluble — a special feature among UV filters, which are mostly lipophilic. In modern cosmetics, extraction and processing are subject to strict quality standards according to EU Cosmetics Regulation (EC) No. 1223/2009. RAU Cosmetics exclusively sources cosmetic-grade raw materials from verified suppliers.

viewBox="0 0 24 24" fill="none" width="32" height="32" aria-hidden="true"> How does BENZOPHENONE-4 work on a cellular level?

Absorbs UV radiation in the UVB range (280-320 nm) and partially in the UVA-II range (320-340 nm) by exciting the aromatic double bonds in the benzophenone skeleton. The absorbed energy is released as harmless heat, preventing the penetration of UV radiation into deeper skin layers. The sulfonate group (-SO3Na) enables solubility in the water phase of the formulation.

viewBox="0 0 24 24" fill="none" width="32" height="32" aria-hidden="true"> Dosage & Regulation

Typical use concentration: 0.5-5% in sun protection products, typically 2-3% for building SPF

How it works on your skin

UVB Protection

Primarily absorbs UVB radiation (280-320 nm), which is responsible for sunburn and direct DNA damage. By converting UV energy into heat, the filter prevents the penetration of this high-energy radiation into living skin cells. Significantly contributes to the SPF (Sun Protection Factor) value.

Water-Phase Stability

The sulfonate group makes this filter one of the few water-soluble organic UV filters. This enables the formulation of light, non-greasy gels, sprays, and lotions without oily residues. Particularly valuable for modern, pleasantly light sun protection products that find high acceptance with daily use.

Formulation Flexibility

Can be used in both the water and oil phases of emulsified systems. This amphiphilicity allows combination with lipophilic UV filters for broad-spectrum protection. Also stabilizes other, more photolabile UV filters in the formulation through synergistic effects.

Indirect Anti-Aging Effect

By blocking UVB radiation, the formation of thymidine dimers in DNA is prevented — the main cause of light-induced skin aging and skin cancer. Long-term, consistent use reduces the risk of premature wrinkle formation, pigment disorders, and actinic keratoses.

Photostability

Benzophenone derivatives are relatively photostable compared to other organic UV filters. They break down more slowly under UV exposure and retain their protective effect longer. This prolongs the effective protection duration of the product during normal exposure.

Who is it for?

Sensitive Skin

Usable as a water-soluble filter in light, non-greasy formulations that put less strain on sensitive skin.

Oily/Combination Skin

Enables light, gel-based sun protection formulations without an oily film — ideal for blemish-prone skin.

Normal Skin

Provides reliable UVB protection in pleasantly light textures for daily use.

In your routine

Apply in the morning after skincare

Apply the sun protection product as the last step of your morning routine — about 1/4 teaspoon (approx. 1.25 ml) for face and neck. Wait 15 minutes before sun exposure so the protective film can fully form.

Dose generously

Most people use only 25-50% of the recommended amount. For sufficient protection, you need about 2 mg/cm² of skin — that corresponds to about 6 teaspoons for the entire body. Applying too thinly halves the actual SPF.

Reapply every 2 hours

Reapply during prolonged sun exposure, after swimming, or heavy sweating. Even waterproof formulations lose significant protection after 80 minutes in the water. For intense UV exposure (beach, mountains), reapply every 90-120 minutes.

Even in winter and with cloudy skies

UVB radiation penetrates clouds up to 80%. Therefore, apply sun protection daily to exposed skin areas even on cloudy days and in winter months. Products containing Benzophenone-4 are ideal for daily use due to their light texture.

Storage: Relatively photostable compared to other organic UV filters (e.g., avobenzone). Optimally stable in a pH range of 6-8. At too high temperatures (>50°C) or storage in direct sunlight, the protective effect can decrease in the long term. Should be kept in opaque or UV-protected packaging. Use within 12 months after opening.

Frequently Asked Questions

Why is Benzophenone-4 water-soluble, while most UV filters are fat-soluble?

The sulfonate group (-SO3Na) on the molecule makes Benzophenone-4 hydrophilic. This ionic group binds strongly to water molecules, while the benzophenone skeleton is responsible for UV absorption. Most other organic UV filters such as avobenzone or octinoxate do not possess such polar groups and are therefore lipophilic. This water-solubility enables the formulation of gels, sprays, and light lotions without an oily film — a major advantage for daily use and consumer acceptance.

Does Benzophenone-4 also protect against UVA radiation?

Benzophenone-4 primarily absorbs UVB radiation (280-320 nm) and only partially the UVA-II range (320-340 nm). For full broad-spectrum protection, it must be combined with UVA filters such as avobenzone, Tinosorb S, or mineral filters (zinc oxide, titanium dioxide). UVA-I radiation (340-400 nm), which is responsible for deeper skin aging, is hardly blocked by Benzophenone-4. Modern sun protection products therefore always contain a combination of several filters for optimal protection.

Can Benzophenone-4 trigger allergic reactions?

Benzophenone derivatives are among the known contact allergens in cosmetics, with Benzophenone-3 (oxybenzone) triggering sensitizations more frequently than Benzophenone-4. However, the allergy rate is low (under 1% of the population). Cross-reactions between different benzophenones are possible. Persons with a known benzophenone allergy should switch to alternative UV filters such as Tinosorb, Uvinul, or mineral filters. For sensitive skin, a patch test is recommended before extensive application.

Is Benzophenone-4 environmentally harmful or coral-bleaching?

The study situation for Benzophenone-4 is less extensive than for Benzophenone-3 (oxybenzone), which was banned in Hawaii and Palau due to coral bleaching. As a water-soluble filter, Benzophenone-4 enters the water more easily than lipophilic filters. Laboratory studies show low bioaccumulation due to the polar structure. Nevertheless, it is debated whether benzophenone derivatives generally have hormone-like (estrogenic) effects on aquatic organisms. To be on the safe side, choose reef-safe alternatives such as zinc oxide (non-nano) or newer organic filters like bemotrizinol.

Why is Benzophenone-4 used less frequently than Benzophenone-3?

Benzophenone-3 (oxybenzone) is more lipophilic and easier to incorporate into classic emulsions, while Benzophenone-4 relies on aqueous formulations or special emulsifier systems. In addition, Benzophenone-3 has a broader absorption spectrum (UVB + more UVA). Benzophenone-4 is preferred in light, gel-based sun protection products, hairsprays with UV protection, or transparent sprays where its water-solubility is a decisive advantage. However, the regulatory discussion about benzophenones in the USA and some island nations is leading to a general decline in both substances.

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