Sunscreen and Sunblock: What's the Difference, Really?

Summer may be coming to an end, but good sun protection should be practiced all year round. Just because you’re not at the beach doesn’t mean you are not exposing your skin harmful sun rays. We are exposed to UV rays all the time, driving in our cars, watching our kids soccer games and sitting on a patio for lunch. Trying to avoid sun exposure during when the sun’s rays are strongest between 10am-4pm is best. However, there are some times that will require you to be in the sun. Follow these tips about sunscreen and sunblock to ensure you are protecting yourself year round. 

Sunscreen and Sunblock are descriptions used interchangeably, but it is important to know that technically they are different products. It is a matter of chemical protection versus physical protection.

Here are some abbreviations you may not know the meaning of:

UV= Ultraviolet referring to radiation.

UVA Rays= Long wavelengths which penetrates skin deeper, the culprits in premature aging, wrinkles and sunspots. Present whether it is sunny or not. UVA rays are weaker than UVB rays, but they can still contribute to skin cancer.

UVB Rays= Slightly more energy than UVA rays, exposure can cause skin to burn and lead to melanoma and other forms of skin cancer.



-Noticeable on skin, most sunblocks leave a thin white-ish layer on skin

-Contains ingredients like Zinc Oxide and Titanium Dioxide which physically block the sun, reflects the rays off skin, almost like a mirror.

-Effective immediately after application because it remains on the skin surface-doesn’t need to be soaked into the skin.

–Deflects UVA and UVB rays, reduces the radiation that hits the skin. 

Chemical Sunscreens:

-Usually appear clear on skin.

-Contains special ingredients that act as chemical filters and reduce ultraviolet radiation penetration to the skin.

-Must be applied at least 30 minutes before sun exposure to soak into skin.

–Absorbs UVB rays.

-Any sunscreen with less than 15 SPF is a waste of time and money.

You may be wondering where spray-on sunscreens fit in. While they are one of the most popular types of sunscreen, I typically advise against them. Yes, they are convenient as can be, but almost no one applies them correctly. To get the level of SPF protection suggested on the can you must apply the sunscreen to dry skin with no wind present and you must apply a LIBERAL amount of the spray to the skin (the skin should look wet) and then you need to rub in the spray into the skin. You then must wait for everything to dry and absorb into the skin before it starts working. Do you know anyone who does all of these steps? While any sunscreen is better than no sunscreen, in general I advise against them. Also, you want to avoid inhaling spray sunscreens as there is still investigation occurring on any potential risk in the lungs.

Bottom Line:

These days, sunscreen and sunblock are so interchangeable, they are not scientific terms to describe sun protection. Many lotions are a combination of both so it is best to look at the labels; mineral ingredients like Titanium Dioxide or Zinc Oxide-those inorganic ingredients physically block the sun. Regardless of whether you use sunblock or sunscreen, they both have the ability to protect you from damaging ultraviolet rays and should be a part of your daily routine.

Erin Jensen, PA-C is a certified Physician Assistant living in Southern California. She pursued her passion for Dermatology after graduating from the USC Keck School of Medicine Physician Assistant Program. On her blog The White Coat Treatment, Erin shares her passion about everything skin, beauty, motherhood, being a Physician Assistant and everything in-between.

Aptly named, Enclothed Cognition is the official Medelita blog for medical professionals interested in topics relevant to a discerning and inquisitive audience. Medelita was founded by a licensed clinician who felt strongly about the connection between focus, poise and appearance.

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