Photocontact Dermatitis

Having sensitive skin can be a real challenge for consumers when it comes to buying cosmetics. It does, however, present an opportunity for cosmetics companies. It is becoming increasingly common for people to consider themselves as having sensitive skin. According to a European study, up to 52% of participants reported sensitivity of some kind. While there are varying degrees of sensitivity, they all amount to a thriving market of products targeting consumers with sensitive skin.

One common cause of sensitive skin is sun exposure. Exposure of the skin to the sun’s harmful UVA & UVB rays will exacerbate skin sensitivity & irritation, so all year-round application of a suitable sunscreen is even more highly recommended than the standard guidelines for sun protection of consumers with non-sensitive skin. This, however, can be problematic for consumers since the inherently complex formulations of sunscreens can cause further aggravation to already sensitive skin. People with sensitive skin often experience irritant contact dermatitis or allergic reactions when using sun care products. They are also at higher risk of experiencing photocontact dermatitis, which is an allergy specific to sunscreen when it is exposed to the sun.


Suncare products are complex formulations with a multitude of ingredients that could irritate sensitive skin. One of the main & most crucial ingredients in sunscreens are UV filters; these are the additives that offer protection from the sun’s UV radiation. There are currently two types of UV filters used in sun care products, chemical & mineral. Chemical filters permeate into the skin where they absorb & dissipate UV rays. Mineral filters form a physical barrier that deflects & scatters UV radiation before it can penetrate the skin.

Chemical filters are more commonly responsible for causing allergic reactions to sunscreen. When the chemicals in the UV filter additive permeate the dermis of the skin, they can cause chemical reactions triggering an immune response that involves mast cells releasing histamine, resulting in inflammation & irritation. Individuals who already have compromised skin due to sensitivity are even more likely to suffer from allergic reactions. Since the chemical filters operate by reacting with UV rays to absorb & dissipate them, they have low photostability. They degrade or destabilise over time when exposed to sunlight, increasing the instances of photocontact dermatitis in consumers.


Simple mechanism of an allergic reaction

While mineral filters are deemed more skin-friendly UV filters, they can still sometimes be problematic, especially for people with sensitive skin. The skin is coated in a layer to form a physical barrier which sometimes means the skin can’t cool naturally & that may cause sensitive skin to react. For example, experiencing prickly heat, which is a condition that occurs when sweat ducts in the skin become blocked & sweat becomes trapped under the skin, resulting in an itchy rash of small, raised red spots.

Mineral filters have more photostability than chemical filters & are the only filters to offer broad-spectrum protection against both UVA & UVB sun rays. The most commonly used mineral filters in sunscreens are Zinc Oxide (ZnO) & Titanium Dioxide (TiO2). Zinc Oxide, a globally approved natural mineral ingredient, is considered the most effective UV filter in broad-spectrum sunscreens.


ZnO currently being used as a UV filter in sunscreens is in one of two conventional forms; of micron or nano particle size. Micron formulations of ZnO contain larger particles in the range of 2 to 10 µm, while in nano formulations the smaller particles range from 10 to 40 nm. Both forms have their advantages & disadvantages. Micron ZnO is commonly considered the safer option by formulators, however, nano ZnO is a more effective sunscreen.

Nano ZnO is more commonly used than micron ZnO by formulators as an effective sunscreen additive. This is due to its higher protection to UV rays per percentage mass & nano ZnO’s ability to cover a higher surface area per percentage mass. It also forms a more visually & aesthetically pleasing sunscreen since it has a high level of transparency. The larger particle size of micron ZnO is what confers its better health & safety profile. The smaller nano ZnO particles may be highly toxic to humans as they may penetrate through human skin.

Comparison of particle size in conventional ZnO forms

micno high spf
micno high spf


Entekno Materials have developed an innovative, novel, mineral-based UV filter, MicNo®-ZnO. Created by the patented MicNo® particle technology chemical & material science process, it has a unique morphology that provides unparalleled UV protection, when compared to currently available UV protection additives. MicNo® particles are scientifically engineered novel platelet shaped micron particles. MicNo® acts like micron ZnO over the skin, since it does not penetrate through the skin, but it still offers the transparent protection of nano ZnO.


How Nano ZnO vs MicNo ZnO work on the skin

Protection from UV rays by percentage mass is much higher for MicNo than both nano & micron ZnO. MicNo also offers a much larger surface area cover per percentage mass; with its novel platelet shape able to cover approximately 70% more surface area than the same amount of nano ZnO, assuming no agglomeration takes place. A low level of uncontrolled agglomeration is another advantage of MicNo over the commercially available versions of ZnO which exhibit uncontrolled agglomeration both in micron & nano forms.

MicNo is designed in such a way that its nanoporous structure creates a continuous coating over the skin with pore channels that make ventilation of the skin efficient. The pore channels even bring a cooling effect to the formulation MicNo is used in, due to this ventilation characteristic. This unique MicNo characteristic will leave end users feeling cooler & more comfortable & could help consumers with sensitive skin avoid adverse reactions caused by bad skin ventilation.


MicNo’s uniquely designed morphology means it exhibits much higher biocompatibility & much less cytotoxicity, genotoxicity & phototoxicity when compared to commercial nano ZnO since it is in the size range of micron ZnO & acts safely on the skin. MicNo® also has excellent antimicrobial properties, exhibiting broad-spectrum antibacterial activity against a range of microorganisms & a number of fungi.


MicNo’s unique nanoporous structure

Harnessing the benefits of micron & nano ZnO, MicNo® provides formulators with a single ingredient for broad-spectrum protection from harmful sun rays. The superior surface covering ability & high SPF ratio per percentage mass means less UV-filter is required by formulators to achieve efficient UV-protection. MicNo’s size means it doesn’t permeate the skin’s epidermis, decreasing the chances of allergic reactions, & its structure ensures much higher photostability. With its broad-spectrum antibacterial activity, MicNo® formulations will also require less or no preservatives. The fewer ingredients required in a formulation the less chance for adverse reactions when the sunscreen comes in contact with the skin, making MicNo the clear choice when looking to formulate skin friendly, high SPF cosmetics for sensitive skin.

MicNo’s non-whitening, high transparency & high dispersion properties, means that not only is it the more efficient, safer & skin friendly option for sunscreen formulations, it also results in the most aesthetically pleasing mineral sunscreen option.

For further information please contact,

T: +90 222 320 36 63
M: +90 554 778 91 45
E: sales[at]enteknomaterials[dot]com

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