Physical and Chemical Sunscreen

Photo: eltaMD , a combination of both physical and 

chemical sunscreen (Source: Amazon)

What's the use of all the promising skin care products if you don't apply sunscreen? After all, it's the sun's harmful UV rays that give you sunburn, dark spots, age spots, and premature wrinkles. Dabbing on some antioxidants on your skin would only give little help if you don't prevent the culprit that has been causing your skin problems in the first place.

Sunscreens are also particularly very useful to people using acne medications such as myself. Topical acne treatment such as benzoyl peroxide and salicylic acid make the skin more sensitive to the sun. Also, sun exposure promotes hyperpigmentation, leading to further darkening of acne marks.

If you are currently looking for a new sunscreen, and have little idea about how to choose one, you might want to check my choosing a sunscreen post first.

There are generally two types of sunscreens, physical and chemical. Each of them works differently to protect your skin.

Physical sunscreens sit on top of your skin to act as a barrier against UV rays. They are very stable under the sun yet leave a noticeably white residue on the skin. Check the ingredients list of your sunscreen. If you see titanium dioxide and/or zinc oxide, it is a physical sunscreen.

Chemical sunscreens, on the other hand, should bind first with your skin in order to become effective. Once taken into the skin (a good 30 minutes), it can protect the skin by absorbing and breaking down the UV rays. However, some chemical sunscreens become unstable when exposed to the sun. In order to make it easier for consumers, the Skin Cancer Organization has tested a wide range of sunscreen products and awarded those who passed their photostability tests with their Seal of Recommendation. Note however that a product without the seal does not automatically mean that it is unstable, only that it might not have been checked by the organization yet.

Unlike physical sunscreens, chemical sunscreens may cause skin irritation and breakouts. That is why if you have sensitive skin, it is advisable that you use physical sunscreen instead. However, many women still prefer to use the latter type because it's more lightweight and visually appealing, not to mention it goes better with makeup. 

Many sunscreens today are a combination of both physical and chemical sunscreen, perhaps because it provides a more photostable and aesthetically appealing formulation. According to Skin Cancer Organization, there are generally at least three UV filters used in a formulation:

1. benzophenones for shorter wavelength UVA

2. PABA derivatives, salicylates, cinnamates for UVB

3. avobenzone, ecamsule, titanium dioxide, zinc oxide for the remaining UVA spectrum

There has been a lot of talks within the skin care community about when to apply sunscreen. It is not uncommon for a woman to apply several products in a day, thereby, the issue of whether the order of sunscreen application can affect it's effectiveness has been a concern.

The common approach suggested is to apply sunscreen last in your skin care routine but before makeup. Meaning, cleanse, tone, moisturize, sunscreen, then primer, foundation, etc. However, other sources recommend applying sunscreen first before anything else. That is, you apply it right after you cleanse and tone your skin. This is specially recommended if you're using a chemical sunscreen, because it needs to bind with your skin to be effective.

Despite the different suggestions, the order of when you should apply it is your choice. If you only believe in scientific studies, there are no such studies yet (at least in my knowledge) that has tested a sunscreen's effectiveness with the consideration of the interaction with other skin care products. As for me, if you really want certainty, then the less products you use at daytime, the better. Save those antioxidant serums and ointments at night.

Haven't decided which sunscreen to buy yet? I have listed here some of the sunscreens that are suitable for oily skin type. On the other hand, if you want to find a sunscreen based on active ingredients, Skinacea has done a great job on classifying these products.

Which type of sunscreen are you using right now? Share what you think about sunscreens.

Last Updated: August 3, 2015