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 : theconversation.com/explain...
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."