Sunscreen is widely acknowledged to protect against sunburn and two common forms of skin cancer, squamous cell carcinoma (SCC) and basal cell carcinoma (BCC). However, there is some evidence that sunscreen use can contribute to negative health outcomes. The major claims include:
- Some sunscreens only protect against UVB radiation, and not against the more dangerous UVA
component of the spectrum. Incomplete protection against the full
ultraviolet spectrum, combined with increased time spent in the sun, can
lead to an increase in the risks of developing malignant melanoma, a rarer but more deadly form of skin cancer.
- Some sunscreen ingredients (including oxybenzone, benzophenone, octocrylene, octyl methoxycinnamate, diisopropyl adipate, retinoic acid, and retinyl palmitate) may be potentially carcinogenic or have other health risks.
- Reduced exposure to ultraviolet light in sunlight can contribute to Vitamin D deficiency.
Studies of melanoma ratesMalignant melanoma has been found more frequently in sunscreen users compared to non-users in some studies. Other studies found fair skinned people used more suncreen and had more skin cancer, but did not address cause and effect. A meta-analysis of 9067 patients from 11 case–control studies found no association between sunscreen use and development of malignant melanoma. It was suggested that sunscreens block the natural warnings and adaptations mediated by UVB, but allow damage from UVA to go unchecked.
Dr Oz has this video on the subject
and some others as well
and do not forget Web MD