With skin cancer incidence on the rise, the number one recommendation by specialists for protection from the sun’s harmful UV rays is sun avoidance. That isn’t always possible though with outdoor occupations & lifestyles. So, in addition to protective clothing, hats & sunglasses, experts suggest that using at least an SPF 15 sunscreen daily could cut down the number of skin cancer cases by 50%.
Sunscreens are one of the most complex & often controversial products in the cosmetics industry. The formulations of sunscreens can vary from product to product, but the most crucial ingredient is the UV filter used. UV filters are the active ingredient that protect you from the sun’s harmful UV rays. They can be classed as mineral or chemical, depending on how they protect from UV rays.
Types of UV filters
Mineral UV filters, also called physical filters, sit on the surface of the skin & act as a physical barrier to UV radiation, blocking & deflecting the UV rays. There are currently two mineral filters in use in sunscreens, Zinc Oxide (ZnO) & Titanium Dioxide (TiO2).
Chemical UV filters permeate into the skin where they absorb UV radiation & disperse it as lower energy heat. Popular chemical filters include oxybenzone, avobenzone, ecamsule, octisalate, octinoxate, octocrylene & homosalate.
Most chemical filters only offer narrow UV protection. The majority of the chemical filters approved by the FDA in the US are good UVB filters, so they protect against sunburn & skin cancer, but are not very efficient UVA filters.
While UVA radiation doesn’t cause any immediate visible symptoms, unlike UVB causing sunburn, it is arguably more damaging. It can penetrate deeper into skin causing skin aging & skin cancer.
Mineral UV filters are generally considered better broad-spectrum filters, with ZnO the only filter recognised to offer equal protection to UVB & the full spectrum of UVA radiation.
Chemical UV filters are more likely to trigger an immune response & cause irritation, itchiness, or an allergic reaction compared to mineral filters. This is because they are absorbed into the skin & have a lower photostability than mineral UV filters, since they absorb UV radiation & their chemical structure converts it to heat, they degrade much quicker.
Recently, chemical filters have also been coming under scrutiny for more serious concerns regarding their absorption into the bloodstream & the possible health implications that may be associated. A recent FDA pilot study found that four common UV filters in suncare products, oxybenzone, avobenzone, ecamsule & octocrylene, were absorbed into the bloodstream after just one day of use of sunscreens containing them & persisted in much higher concentrations than was anticipated. These results prompted the FDA to call for further testing to establish their safety.
In fact, in the latest proposed rule by the FDA for sunscreen safety, only the two mineral UV filters ZnO & TiO2 were left in the GRASE (generally recognised as safe & effective) category. Two chemical filters, PABA & trolamine salicylate, are now considered unsafe, while the remaining 12 require additional clinical & non-clinical data before they can be given a classification.
A number of chemical filters are also suspected of interfering with hormone levels, acting as endocrine disruptors. In animal studies, some chemical filters including oxybenzone, homosalate, octinoxate & octyl-methoxycinnamate were found to affect thyroid & reproductive hormones. Oxybenzone & octinoxate are also considered harmful to marine ecosystems & sunscreens containing them have been banned in some places around the world, such as Hawaii & Palau.
Why favour mineral filters
Mineral UV filters not only offer broader protection to both UVA & UVB rays they are also faster acting, stable & safe. They remain on the surface of the skin, so begin protecting against the sun’s rays as soon as the sunscreen containing them is applied, while chemical sunscreens need about 20 minutes to be absorbed into the skin before they effectively protect against the sun.
Mineral UV filters are also much more photostable than chemical filters as they structurally deflect the UV radiation without chemically interacting with it. This higher photostability, means they are effective in protecting against the dangerous UV radiation for longer without needing reapplying, provided you have not gotten wet or sweated excessively which could cause the sunscreen to wipe off. This higher photostability also decreases the instances of irritation or allergic reactions.
Traditionally, mineral sunscreens have been associated with heavier & thicker formulations that do not spread as easily on the skin & leave a white cast, especially ZnO. So, while ZnO is considered the safest & best broad-spectrum UV filter it was often not preferred by consumers. Great progress has been made in sunscreen formulations to decrease this white cast effect, predominantly by using smaller particle sizes in the nanometre range.
Nano mineral UV filters offer better SPF & transparency, however, concerns over the health implications of nanoparticles have caused apprehension for products containing mineral UV filters in the nano range. While some studies suggest that in large doses nanoparticles can harm humans, the latest research suggests that nano ZnO in sunscreens cannot penetrate the skin in any significant amount. Another study found that when exposed to ZnO nanoparticles, human immune cells effectively absorbed the nanoparticles & broke them down. Nanoparticles can cause lung damage when inhaled though, so they are not recommended in spray or powder sunscreens.
ZnO is currently used in sunscreens in micron (2 to 10 µm) form as well as nano. Micron ZnO is associated with a better safety profile but is less transparent than nano ZnO, so nano ZnO is often favoured by sunscreen formulators.
MicNo®, a novel ZnO UV filter
Entekno Materials has designed & developed innovative MicNo® ZnO Particle Technology to allow sunscreen formulators to overcome the disadvantages associated with micron & nano size of ZnO used as a UV filter in sunscreen products. MicNo is a single novel ingredient with the added value of,
UVA, UVB & Blue Light protection
High SPF ratio per % mass
Excellent dispersion properties
Opportunity for formulations to be preservative free
Green lights to proceed with MicNo
Using patented MicNo particle technology, Entekno were able to produce tailored, platelet shaped, micron sized particles composed of nano ZnO primary particles. With its unique design, the MicNo particle can harness the benefits & overcome the problems associated with the conventional micron & nano ZnO forms currently used in sunscreens. MicNo particles behave like safe micron particles over the skin & transparent nano particles under the light.
Its novel design means that MicNo can not only offer an even better protection against the sun’s UV rays than conventional nano ZnO, while still maintaining the safety of micron ZnO, but it can also go a long way towards making mineral sunscreens much more aesthetically & visually pleasing.
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