Something I've been wondering recently: is sunscreen application to the lips necessary, safe and/or effective.
It seems there could be something different about the lips and the way they respond to sun exposure compared to most other skin. I can never recall experiencing sunburn on my lips, nor can I recall anyone I know suffering sunburnt lips, despite not applying sunscreen to them. That's not to say that lips aren't potentially damaged by sun exposure though. I have yet to search the peer review literature on this topic, but I have seen anecdotes on the web of suburnt lips, and opaque white zinc has been made and used specifically for lips.
Second, is it safe to apply sunscreen to lips? There's already been a lot of controversy surrounding the safety of sunscreen on non-lip skin, with a substantial focuse on the issue of (transcutaneous) absorption. Applying sunscreen to the lips would seem to likely to lead to some direct ingestion of the sunscreen, which might result in increased absorption and systemic exposure. Many sunscreens also have warnings to the effect of "For external use only." which could raise some concerns. There are also many so-called "non-active" chemical ingredients in sunscreens that may need to be considered when trying to determine their lip safety.
Third, how long would sunscreen be expected to stay on the lips? The lips are constantly exposed to moisture and friction just by default, in addition to regular eating and drinking. Most sunscreen suggest to reapply after sweating or towelling, so is it reasonable to expect sunscreen to survive on the lips for long? If sunscreen has to be frequently re-applied to the lips, could this further magnify safety concerns?
What are your experiences, thoughts, practices etc on this issue?
Edited by Brett Black, 12 April 2016 - 03:38 AM.