There are two broad types of sunscreen products categorized according to their mode of action. Both provide protection against the adverse effects of UV radiation such as sunburns, photoaging, and skin cancer. It is also important to mention that the term “sunblock” was used in contrast to “sunscreen” to distinguish two different ways topical skincare products protect the skin from ultraviolet radiation work. However, “sunblock” is now an outdated term, and in the United States, it is a prohibited label since 2011.
The Difference Between Physical Sunscreen and Chemical Sunscreen
Most of the literature now consider “physical sunscreen” and “chemical sunscreen” as the two broad categories or types of sunscreens. Accordingly, products containing inorganic compounds that deflect UVA and UVB radiation are considered “physical.” Two widely used ingredients in physical sunscreens are titanium dioxide and zinc oxide.
On the other hand, organic particulates are the main active ingredients in chemical sunscreens. Instead of deflection, they work by absorbing and neutralizing UVA and UVB radiation before they penetrate the skin. Examples of these particulates include avobenzone, octisalate, octocrylene, oxybenzone, homosalate, and octinoxate.
Note that “sunblock” was the outdated term for skincare products designed against the harmful radiation from the sun by providing a physical barrier on the skin. The U.S. Food and Drug Administration has banned manufacturers from using this term in their labels and marketing. Nevertheless, how a specific sunscreen works would depend on the type of active ingredients used in the formulation.
Below are further details to compare the difference between physical sunscreen and chemical sunscreen:
Physical Sunscreens
• Mode of Action: They work by leaving a thin physical barrier on the skin that mainly reflects and/or scatters, as well as absorbs ultraviolet radiation, thus preventing UVA and UVB from penetrating deeper into the skin.
• Application and Duration: Physical sunscreens should be applied 20 minutes before exposure to the sun to give the formulation time to settle on top of the skin. Furthermore, they should be reapplied every 2 hours or less.
• Variations and Availability: Some products protect from UVB only while others provide broad-spectrum protection against both UVA and UVB. It is essential to check the sun protection factor or SPF for UVB protection, and UVA protection factor or UVA FP and UVA Protection Grade or UVA PA.
• Overall Description: These products are generally thick and opaque, thus making them harder to spread on the skin and are difficult to wash off. They also tend to leave a white cast on the skin. Most physical sunscreens are available in lotion formulation, although there are formulations available in liquids and liquid sprays.
Chemical Sunscreens
• Mode of Action: They work by leaving a thin film of formulation on the skin that includes a combination of active ingredients that absorb and neutralize ultraviolet radiation before it penetrates the skin.
• Application and Duration: Similar to physical sunscreens, chemical sunscreens should be applied before going outside or prior to sun exposure. They usually take 15 minutes after application to be effective. Reapplication every 2 hours or less is necessary because some of the active ingredients break down due to sun exposure.
• Variations and Availability: Different organic particulates provide different chemical and specific absorbent properties. It is best to choose a broad-spectrum UVA and UVB chemical sunscreen as determined by its SPF rating and UVA FP or UVA PA grade.
• Overall Description: This type of sunscreen is available in different formulation variations, including lotions, liquids, and sprays. They are also easier to integrate into other skincare products such as facial moisturizers, toners, liquid makeup, and hair leave-on products and hairsprays, among others. Chemical sunscreens are easier to rub and are usually transparent.
Choosing Between Physical and Chemical Sunscreens
There is no better option between the two categories or types of sunscreen in general. It is best for consumers to look for a product that provides broad-spectrum protection against UVA and UVB. The SPF rating should be at least 30, and the UVA protection rating or grade should be indicated in the label.
Choosing between physical sunscreen and chemical sunscreen is a matter of preference. Some do not like the white cast that comes from products based on zinc oxide and titanium dioxide. Also, there are specific types of skincare products that are better formulated using organic chemicals that absorb ultraviolet radiation.
However, it is also worth mentioning that products with zinc oxide or titanium dioxide may be less irritating, thereby a good choice for those with sensitive skin, as well as for babies and toddlers. Zinc oxide also has limited antimicrobial properties and calming effects on the skin, while titanium dioxide is the least expensive sunscreen ingredient available.
FURTHER READINGS AND REFERENCES
- Kuritzky, L. A. and Beecker, J. 2015. “Sunscreens.” Canadian Medical Association Journal. 187(13): E419. DOI: 1503/cmaj.150258
- Latha, M. S., Martis, J., Shobha, V., Shinde, R. S., Bangera, S., Krishnankutty, B., Varughese, S., Rao, P., and Kumar, B. R. N. 2013. The Journal of Clinical and Aesthetic Dermatology. 6(1): 16-26. PMID: 23320122