Shabbat: Sunscreens

To use a fluid on skin on Shabbat, even sunscreen that may be needed to protect damaged skin, it must flow without lumps and not be more viscous than honey at room temperature. Therefore, apply sunscreen only if fluid (but not a cream or thick liquid).
Note You may dilute sunscreen before Shabbat with water or alcohol, but some sunscreens do not become more fluid even with added water or alcohol.
Note On Shabbat, you may use oil for pleasure, such as for massage, but not for refu'a/healing purposes, such as to heal chapped skin.