Sunscreen: Chemical vs. Physical

Sunscreen (sunblock, suntan lotion, sun cream or what ever else you have heard it called) is meant to protect your skin from potentially harmful UVA and UVB rays. These ultraviolet rays are what cause sunburn. Most sunburns are the result of overexposure to UVB rays (260-320nm in sunlight).

For maximum protection from UV rays, it is important to apply sunscreen about 20 minutes before you go outside, and to reapply it every two hours. However, if you are going in the water, you should apply more often as water resistant sunscreens only protect for between 40 and 80 minutes.

There are two different types of sunscreens: chemical and physical.

Chemical:

Chemical sunscreens contain ingredients that actually absorb UV rays. Some common ingredients in these sunscreens are avobenzone, oxybenzone, Tinosorb M, Tinosorb S, Mexoryl SX, and Mexoryl XL. These ingredients absorb harmful UV rays and convert them into harmless energy. Ingredients like Tinosorb M and S and Mexoryl SX and XL protect skin from both UVA and UVB rays.

If you plan on using sunscreen containing avobenzone make sure that it also contains a stabilizing ingredient like octocrylene. Avobenzone needs to be stabilized because it degrades when it comes in contact with sunlight. About 56% of beach and sport sunscreens contain oxybenzone according to the Environmental Working Group (EGW).

Many toxicology experts believe that oxybenzone is an unsafe ingredient that can lead to hormone disruption and cell damage. Here is an article discussing exactly that. It is suggested that children avoid using sunscreens containing oxybenzone until more research is done.

Physical:

Physical sunscreens usually contain particles of zinc oxide or titanium dioxide which sit on the surface of your skin and deflect UV rays. The size of these ingredients is usually 20 to 200 nanometers.

A possible problem with this type of sunscreen, according to new research from the Missouri University of Science and Technology, is that a chemical reaction happens when zinc oxide is exposed to sunlight. This chemical reaction produces free radicals that may increase risk of developing cancer because these unstable molecules can cause damage to cells and their DNA as well as kill them entirely. The longer zinc oxide is exposed to the sun, the more it can cause damage to cells. However, the scientist who conducted this research, Dr. Yinfa Ma would "still advise people to wear sunscreen. Sunscreen is better than no protection at all."

Today, sunscreen is available in both creams and sprays. However, the EWG does not endorse the use of spray-on sunscreen as the nanoparticles of these metal oxides can be inhaled and their effect on our bodies is not yet known.

So if so many of the ingredients in these sunscreens are potentially bad for our bodies, what should we do?

Interestingly enough, different foods can actually increase your internal sun resistance. Foods containing a lot of antioxidants as well as super foods help with this. Astaxanthin, a dietary supplement, contains fat-soluble carotenoids that are carried to skin cells to protect the cells from UV exposure. There are also natural sunscreen products for sale, although the FDA does not allow them to be labeled as sunscreen, that may be safer for your skin!

Katie Rigdon

Sources:

http://news.mst.edu/2012/05/sunscreen_ingredient_may_pose.html

http://www.medicalnewstoday.com/articles/176441.php

https://www.pharmacymix.com/physical-vs-chemical-sunscreens.htm

http://www.naturalnews.com/032815_sunscreen_chemicals.html

How do skin lighteners work? Arbutin's role in cosmetics

At one point or another we've all seen our mothers or grandmothers dabbing their face with cream. Look inside their purse and you'll find a small container called "Skin Lightening Cream" boasting to "get rid of all your dark spots to make you look 10 years younger!" Have you ever stopped to ask yourself just how these creams can lighten your skin? Well many utilize a chemical called arbutin to aid in this effort. Arbutin inhibits the enzyme tyrosinase - an enzyme that controls the synthesis of melanin. Inhibit this enzyme and produce less melanin, thus making less pigment and lightening the skin.

Structure of tyrosinase 

Simply put, arbutin is a chemical with a glucose attached to a hydroquinone - an organic compound featuring two hydroxyl groups bonded to a benzene ring.

Arbutin - glucose and hydroquinone

Hydroquinone

However, it is important to understand that there are different types of glycosidic bonds between the glucose and hydroquinone that produce different behaviors of the chemical - namely, alpha and beta. Beta is the one that occurs naturally in the bearberry plant from which arbutin is extracted. Glucose residues in cellulose are bound by beta glycosidic linkages while glucose residues in starch are bound by alpha glycosidic linkages. Naturally extracted "beta" arbutin is common among the world of cosmetics while the "alpha" arbutin can only be produced in laboratories. 

A common point of contention among scientists today is "Is new always better?" Yes, we've have managed to engineer an alpha arbutin - but is it necessarily better than the naturally occuring beta? In fact, it would be false to suggest that merely because it is new it provides better suppression of melanin than the beta while staying just as safe as the naturally occurring arbutin. Until full toxicological tests are performed on the new chemical with positive results should the shift be made towards the new alpha arbutin as the most common skin lightening agent. It is in the opinion of Hannah Sivak, PhD that "novelty in a chemical is not an advantage but a problem."

Source: http://www.skinactives.com/blog/2011/04/28/guide-what-is-arbutin-the-most-common-skin-lightener/


andrew kang