According to the great majority of authorities, human nursing, not only milking a cow, is a Torah violation of mefarek,[1] at least in many cases. We obviously allow a baby to nurse on Shabbat, but usually it is the baby who performs the very important, “problematic” act. Is it permissible for a woman to express milk for her baby’s needs in general, or, in this case, for medicinal purposes?
The Shulchan Aruch[2] says that a nursing mother may not express milk into a cup to feed her child. (It is permitted to express to relieve an oversupply in such a manner that the milk is lost immediately[3]). However, there are instances in which expressing milk with the aim of it being used is permitted. They may shed light on our case.
The Shulchan Aruch[4] rules that a woman may express milk into her baby’s mouth[5] in order to interest him in nursing. Most poskim understand that this is not a level of need that we would consider life threatening. Why, then, is it permitted? Similarly, the Shibolei HaLeket[6] says that a woman may not squirt her milk on someone who is under the influence of a strange malady, because the situation entails neither danger nor extreme pain. This implies that it would be permitted in the presence of such pain. Why?
The Magen Avraham[7] and Mishna Berura[8] explain the implied leniency by claiming that this expressing of milk is a melacha she’eina tzricha l’gufa, which usually means that the end result of the Shabbat violation is not used in a classical, positive way. Since this classification reduces the act to a Rabbinic violation, it is then permitted on Shabbat to relieve significant pain.[9] While it is difficult to understand how the category of melacha she’eina tzricha l’gufa applies in the rulings above,[10] it is hard to dismiss an approach posited by such prominent proponents, and their leniency seems to apply to your case. (Even non-illness needs of a small child, let alone medical situations, are considered equivalent to those of sick adults.[11]) In fact, the Kaf HaChayim[12] writes, based on the above, that a woman may express milk into the ear of someone with a serious earache (assuming it has therapeutic value).
The Tosefet Shabbat,[13] not seeing a melacha she’eina tzricha l’gufa in the above, suggests a different reason for the leniency – expressing milk from a woman in a manner other than nursing is an unusual form of mefarek, and is thus only a Rabbinic prohibition, just as a human “nursing” from a cow is.[14] According to this approach, your case would also be permitted. (The Mishna Berura finds the Tosefet Shabbat’s approach difficult.[15]) Other possible grounds for leniency relate to the small amount of milk that is expressed and that it is being used immediately. These points apply to your case as well.[16]
While each explanation has its weakness, the fact that so many of them permit your case is of great importance.[17]
We have established significant grounds to permit the pediatrician’s suggestion, although it is far from clear cut.[18] Since the eye is an area with regard to which Halacha tends to be lenient at the mildest possibility of danger,[19] and since we are also very careful regarding such a young baby, we would be lenient in this case if there were any medical preference for using mother’s milk as a medical therapy. However, you indicate that the doctor does not really favor the mother’s milk idea over other effective available medicinal alternatives. Therefore, it is halachically preferable – because of doubt and because it is better to avoid the Rabbinic mefarek violation when there are good alternatives – to not use the system of expressing mother’s milk into the eye on Shabbat.