Sunscreen on Shabbos
As the summer heats up and people spend more time outdoors, we must consider the halachic ramifications of applying sunscreen on Shabbos. Ostensibly, two potential issues prohibit smearing sunscreen on Shabbos: refua and memacheik (smoothing something out); however, we will see that one may be allowed to apply sunscreen on Shabbos.
Acts of refua and healing were prohibited on Shabbos by a Rabbinic decree out of concern that one may come to violate Shabbos by grinding medicinal herbs. The Mechaber (328) rules based on a Yerushalmi that this only applies to medicines with healing effects, not items that merely prevent dangers. (This is why it is permissible to use a bandage that simply protects the open wound but not a vine leaf that the Gemara says contains healing properties actually to help the wound close.) Accordingly, sunscreen that only blocks the UV rays from damaging the skin, but does not heal the skin would not be forbidden because of refua. (Rabbi Sprung warns that certain specialized sunscreens for people with sensitive skin would be assur because it would be considered refua.)
Additionally, there are ways to circumvent the memacheik issue as well. The Biblical prohibition of memacheik is to smooth out a substance (wax on a barrel). However, it only applies to a thicker consistency like wax, not liquids such as oil. Many Rishonim posit that there is a Rabbinic prohibition against spreading creams onto one’s skin. However, Shmiras Shabbos Kihilchosa says in the name of the Chazon Ish that one may smear a cream when one intends for the cream to be completely absorbed in the skin as this is different from memacheik where the smeared substance is visible above the original surface. While R’ Shlomo Zalman and R Ovadia Yosef ruled similarly, they disagreed about the technicalities of how sure one must be to rub all the sunscreen into the skin.
To summarize, there is no concern about refua when applying sunscreen, and to avoid any issues of memacheik, one should preferably use liquid sunscreen. If that is not available, it is permissible to apply sunscreen on Shabbos so long as one is sure all the sunscreen is absorbed into the skin. With that in mind, we will be fully and properly protected from the sun’s damaging rays.
Adapted from medicalhalacha.org