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Checking for Lice on the Sabbath

March 9, 2015

Question: Lice on Shabbos: Anything to do about it or must treatment be continued after Shabbos?

Answer: Concerning checking for lice on Shabbos:

1. The sages of the Talmud did permit killing creatures such as lice on the Sabbath. This was on the assumption that lice do not sexually reproduce and are therefore not truly alive. Now, we know better. How should this affect the halacha? See here for many of the sources. I believe that although we can not say that killing lice is as forbidden as killing larger animals, it never the less has the force of a rabbinic prohibition today. That is, had Hazal been around to know what we know, they either would have declared the killing of lice to be included in the Torah prohibition, or they would have made it a rabbinic prohibition because of its similarity to the Torah prohibition. As for the claim that because the sexual reproduction practiced by lice is not visible to the normal human eye, lice are halachically considered as not to be sexually reproductive, it is not so. Yes, it is true that up until the modern era no one saw lice mating, but that is because they did not know how and where to look. However, nowadays it is very easy to see it happen, without the aid of microscopes, if one were to isolate male and female lice. Here‘s one of many youtube videos of the subject. I still believe that there are certain species, like copepods, that are so small that it is only through the aid of technology that we can tell that they do engage in intercourse. I think it is disingenuous and dishonest to say that it is still permissible to kill lice on the Sabbath.

2. Checking for lice until the modern era meant removing the larger, easily visible lice from a person’s hair. It was as simple as lifting ants off of a table. Today, when women have to go through their children’s hair with a special fine-toothed comb to remove the young lice and eggs, they are doing more than our sages ever imagined, because our sages were unaware that those minuscule particles the women find are the lice and eggs themselves. The modern act of checking for lice is therefore:

a. either forbidden as a derivative labor of nipputz, combing wool or linen, as understood by many early authorities. (Maimonides did not define nipputz in that manner.)

b. or forbidden as a derivative of borer, selecting (Laws of Sabbath, 8:12):

A person who separates food from unwanted matter and one who separates one type of food from another food using a sifter or a strainer is liable. If one separates using a tray or a pot with compartments, one is not liable. It is permitted to separate food by hand to eat immediately.

Recall that with regards to this law, “food” refers to the part of the mixture that is desired, and not necessarily something edible. See also that halacha 14 stresses the fact using a specialty tool to separate the unwanted component of the mixture is a critical component of the prohibition.

c. or forbidden as a taxing manual exercise. There are many halachoth you can find where the sages’ goal was “so that it not be done like on a weekday. As I wrote above, lice checking used to be a simple task; what we do today is meticulous.

3. One might suggest that checking for lice also requires direct and powerful light, and our sages prohibited, for example, reading by candle light lest one come to tilt the candle and cause it to burn brighter. We do read on the Sabbath because our home light fixtures are attached to the walls or ceilings and are usually unadjustable, and therefore it is not likely that someone will attempt to brighten them inadvertently in the course of reading at home. However, and you have seen this from personal experience, when our wives check the children for lice, they specifically bring over the brightest lamp they can find and purposely direct its light on the child’s head. My fear is that they may come to do same on the Sabbath.

In light of all of this, I instruct my wife and anyone who else who asks to 1. not check children for lice on the Sabbath, and 2. to not take advantage of the sages’ dispensation and kill really small bugs, like lice, on the Sabbath, unless out of necessity.

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