Hi Chloe,
I read this book from adrian Jones. He calls the black salve the natural scalpel. Let me quote him: Translated feom the dutch book.
It is possible that some kind of suncream cause cancer. The creams contain benzofenon (or derivates of this) and this belongs to the free radicals, activated by sunlight and is known as a carcinogene agens. Other substances contain nitrosamines and cinnamates absorbed by the skin and contaminating the skin, as well as internal organs and tissues. It might be possible to cause skin cancer and in the scientific world one becomes more and more aware.
It is confusing, Chloe, since we got raised to protect yourself with cream and now it is the other way around. However there are some healthy alternatives. Lavera has creams in my country. You will find some in the Eko stores.
Best is to avoid sun between 12 and 16. In tropical countries peoples do this spontaneous. Sungazing only when it feels comfortable...