CLL Support Association

Explainer: how does sunscreen work

Explainer: how does sunscreen work

Our compromised immune systems put us at considerably higher risk of skin cancers, (upwards of 10 times), so we have much to gain from learning how to protect our skin from sun exposure. This easy to read article by Terry Slevin of Curtin University and Cancer Council Australia explains how sun screens work and how best to use them effectively :

Note in particular:

"Recent research suggests the longer UVA wavelengths not only penetrate to deeper layers of the skin but contribute to skin cancer through compromising immune response to DNA damage.

For that reason, sunscreen labelled “broad spectrum” is recommended as it offers the best protection."

Meanwhile Medpage today reports the results of two trials assessing the promise of fluorouracil and nicotinamide in reducing the incidence of squamous cell carcinoma and basal cell carcinoma in high risk populations - with mixed results:

"A randomized trial of 932 veterans at high risk for keratinocyte carcinoma showed that topical fluorouracil, 5%, applied twice daily to the face and ears for up to four weeks, reduced the risk of squamous cell carcinoma (SCC) requiring surgery by 75% in the first year after use (risk ratio 0.25, P=0.002), researchers found.

Risk of basal cell carcinoma (BCC), however, was similar at about 10% in the first year in the fluorouracil group and in controls, reported Martin A. Weinstock, MD, PhD, of Providence Veterans Affairs Medical Center in Rhode Island, and colleagues online in JAMA Dermatology."


"A randomized study has shown that daily ingestion of a large dose of nicotinamide (NNA) can reduce the risk of SCC and BCC by 23%. However, this beneficial effect disappears as soon as dosing stops, Weinstock and colleagues said. Notably, the results indicated that nicotinamide may simultaneously increase the risk of the most aggressive types of BCC and SCC."


5 Replies

For some reason the article about sunscreen did not come up for me. But I also have a “wonder?” About past sun damage to the DNA. My hubby grew up a surfer, athlete in Florida with skin that tanned easily. So since 7th grade until a few year ago, kept a fairly dark tan. I guess only time will tell what his immune system will do with that. He does see the dermatologist once a year. And had a tiny bit of his nose removed. He uses sunscreen (broad spectrum) daily now.



The link did not go to a discussion about sun screen.



The link worked for me - went straight to an article about Sunscreen.

Paula (in the UK)


My post has now been corrected and updated with reference to a relevant Medpage Today article.

Thanks Dennis and Linda (Spacee and Fant1924), for letting me know the link didn't work. I missed copying the last character of the link and with The Conversation website, you can end up viewing articles at random then. :)



Some important information I have learned through the years include:

- surface block is best with proper clothing, or sunscreen containing titanium dioxide (leaves a white chalky appearance)

- choose chemical block sunscreen containing Avobenzene which blocks UVA; almost anything blocks B, including clouds

- check all skin conditions using the alphabet;

*A asymmetric look of condition; consistent is best

*B smooth border all around

*C consistent color throughout; dark and varied is least desirable

*D diameter no more than a pencil eraser

*E elevation is not increasing. This one is especially important

* choose sunscreen that is at least spf 30 that blocks uva and uvb; there is little need to use a higher spf since 30 blocks about 97%

- wear a wide brim hat

Dennis, 70, Ibrutinib


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