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Parashas Shemini – Halachos of Bugs in Food

A Jew is distinct in many ways from the other nations of the world. One facet which sets the Jewish People apart from the other nations is the food we are allowed to consume. This week’s parashah deals with the laws of kashrus, delineating which animals, fowl, fish and other creatures, are kosher, and which are not. Although other laws of kashrus are recorded elsewhere, the laws in our parasha serve as the base for the Jewish guide to kosher consumption.

Special Stringencies of Bugs

Among the laws of kashrus, the Torah mentions the prohibition of eating insects (Vayikra 11:41): “Every swarming thing that swarms upon the earth is detestable; it shall not be eaten.” The verse continues to explain that all forms of bugs are included in the prohibition: “All that goes upon the belly, and all that goes on all fours, or all that has many feet—even all swarming things that swarm upon the earth—you shall not eat them, for they are a detestable thing.”  Worms, spiders, centipedes, flies of all sorts and so on, are all prohibited.

The Torah concludes this chapter by stressing the gravity of this prohibition, which defiles the consumer (Vayikra 11:45):  “For I am Hashem who brought you up (hama’aleh) from the land of Egypt, to be your G-d; you shall therefore be holy, for I am holy.” Dwelling on the word hama’aleh, which is written specifically in connection with this prohibition, the Gemara (Bava Metzia 61b) writes that the prohibition of bugs is sufficient—in itself—to justify the redemption of the Jewish people from Egypt. The Gemara writes further that even though the redemption is mentioned in connection with other mitzvos, the consumption of bugs is considered disgusting, and the holiness of Israel obligates separation from such lowly things.

Another indication of the severity of the prohibition to eat bugs is that the sin of consuming insects is increased by repeated mention in the Torah. Whereas one who consumes the meat of a non-kosher animal transgresses a single Torah prohibition, one who consumes an insect transgresses four, five or possibly six Torah transgressions! (The precise number depends on the type of insect; see Makos 16b, and Aruch Hashulchan, Yoreh De’ah 84:13-14).

It should be noted that not all insects are actually prohibited. Based on the words “every swarming thing that swarms upon the earth,” the Gemara (Chulin 67a) states that only bugs that have walked on land are prohibited. This implies that bugs formed and found (meaning that they have never departed from their place of origin) within a detached fruit (which, unlike a fruit still on a tree, is not considered ‘on land’), or formed and found inside the flesh of a fish, are not prohibited. This halachah is the source of the controversy that recently erupted over anisakis worms in the flesh of fish, the debate centering on whether or not the worms leave their place of origin.

In this article we will not discuss the intricacies of bug classification, but rather set out guidelines for the halachos of insect prohibition.

Small Amounts: the Kezayis Issue

In general, Torah food-related prohibitions depend on the consumption of a fixed amount—a kezayis (the volume of an olive). Although it is forbidden to eat even a smaller amount, one does not transgress the full Torah prohibition unless he has eaten a full kezayis.

However, with regard to bugs, the halachah is often different and a person transgresses the full prohibition, even if the bug he eats is a single millimeter long. The reason for this is that provided the bug remains complete, the bug has the halachic status of a beriah, a complete entity. Its consumption therefore involves a full Torah prohibition despite its miniature size (Makos 16b; Rambam, Laws of Forbidden Foods 2:24).

Aruch Hashulchan (Yoreh De’ah 84:12) thus warns: “One who eats a whole fly or mosquito and so on, be it alive or dead, transgresses the prohibition of consuming a winged insect even if it is smaller than a kezayis. This is the halachah for all types of bugs.”

Laws of Annulment in Mixtures

Another stringency that emerges from the status of a bug as a beriah applies to laws of annulment (bittul). For most forbidden foods the general laws of annulment apply, meaning that if forbidden and permitted foods are mixed up, and the amount of the permitted food exceeds the forbidden food by at least sixty to one, the forbidden food is nullified and consumption of  the mixture is permitted. Thus, if a small piece of non-kosher meat falls into a pot with many pieces of kosher meat (and gets lost therein) and the amount of kosher meat is sixty times more than the non-kosher piece, the entire mixture is kosher.

Bugs, however, have the status of a beriah and are therefore not annulled even in one thousand times their own volume. If a whole insect falls into a pot of kosher food and gets lost therein, the entire dish will be prohibited (Shulchan Aruch, Yoreh De’ah 100:1).

For instance, if a gnat falls into a pot of potatoes and gets lost therein, the potatoes may not be eaten unless one ensures (by cleaning off each potato) that the gnat is not present in the food he is putting into his mouth. Similarly, if the gnat falls into a pot of soup, the soup will need to be strained through a fine strainer, to ensure that the gnat is not in the soup, before it may be eaten (Shulchan Aruch, Yoreh De’ah 100:2).

Annulment of Chopped Bugs

The principles outlined above apply to whole bugs, but not to bugs that have been chopped up. If a bug has been chopped up, it no longer retains the status of a beriah, and the regular laws of annulment apply.

For this reason, there is no obligation to separate insects from grains of wheat prior to grinding it. Because any bugs in the wheat will be ground together with the wheat itself, and there is no chance that a whole bug will remain in the flour,  one can rely on the annulment of the bug in the far greater quantity of flour (Shulchan Aruch, Yoreh De’ah 84:14).

This halachah appears to clash with a known halachic principle, whereby “one may not purposely annul a prohibition.” This means that it is forbidden to intentionally cause a prohibited food to be annulled, and the laws of annulment may only be relied on in a post factum scenario. Based on this principle, one would seemingly be obligated to ascertain that the wheat is insect-free prior to grinding; otherwise, one surely causes their annulment intentionally?

The Terumas Hadeshen responds to this question by stating that due to a combination of factors grinding unchecked wheat is permitted. One factor is that we are not certain that bugs are present in the wheat, because it is possible that they leave the wheat upon hearing the sound of the grinding wheel. A second factor is that the grinding is not done with the intention of annulling the bugs in the wheat, but rather for the purpose of producing flour, the grinding of bugs being only a side-effect (see Shach 84:40).

Yet, Taz (99:7) rules that this leniency is not absolute, and it is only permitted to grind the produce (and the bugs therein) when cleaning is impossible. Pischei Teshuvah (99:4, quoting from Peri Megadim and others) explains that this exclusion applies not only to cases wherein it is impossible to clean the produce, but even to cases in which substantial effort and trouble are involved.

Thus, it is permitted to grind grapes (in wine production) or other fruit (in production of juices), without prior checking for bugs, wherever checking and cleaning would constitute a major effort. Provided there is no definite infestation and provided that one’s intention is not for the sake of grinding bugs (but rather for making wine or juice), the annulment of the bugs is a permitted side-effect of the grinding.

In domestic settings, the trouble involved in checking and cleaning is usually not substantial, and under most circumstances one is obligated to check and clean food, rather than just chop or grind the food. It is only for foods that are especially difficult to check and which need to be ground in any case, that one may grind the food, after ensuring that there is no definite infestation (by means of basic cleaning).

Poskim rule further that in case a food is extremely difficult to check one may take steps to minimize the possibility of remaining bugs and then grind up the food—even when one’s intention is to ensure the kashrus of the food. For instance, it is permitted to wash parsley leaves thoroughly with soap and water and then finely chop the leaves in a blender. Similar advice is given concerning broccoli, cauliflower and other vegetables that are hard to verify as bug-free (see Bedikas Hamazon Kehalachah, Vol. 1, p. 140).

Tiny Bugs

The Gemara teaches that “The Torah was not given to ministering angels.” This means that the Torah was given in accordance with human limitations, and we are not expected to perform the Torah to a degree that transcends human capabilities. Authorities derive from this principle that there is no prohibition of consuming bugs that cannot be seen by the naked eye.

The Binas Adam (34) quotes from Sefer Habris that it is forbidden to consume vinegar, because scientists discovered that vinegar is full of ‘bugs’ that can be seen through a magnifying glass. The Binas Adam rejects this opinion, writing that there is no transgression in eating bugs that are invisible to the naked eye. This ruling is the undisputed consensus of later poskim (see Aruch Hashulchan 84:36; Machazeh Eliyahu 91).

Yet, it is important to clarify that the leniency of eating ‘invisible bugs’ applies only to those bugs that are truly invisible. If a bug can be seen by holding it up against the sun or against a dark or bright background, then the fact that the bug is camouflaged by its environment (for example, a greenfly on a lettuce leaf) does not permit its consumption. This principle is stated by the Bach (84) with regard to bugs that can only be seen by holding something up to the sun, and reiterated by the She’elas Ya’avatz (2:124) concerning bugs in rice. The fact that a bug is difficult to discern does not render it permitted for consumption.

Not all eyes are identical, and some people’s eyesight is stronger than others. Whose sight does the visibility and halachic status of bugs depend on? The Chasam Sofer (Orach Chaim 132) writes that even bugs that cannot be discerned by those possessing ‘weak vision’ are prohibited, and it is therefore important to ensure that food is checked by somebody with proper eyesight.  Moreover, the Darkei Teshuvah (84:15) says that unless the bug is invisible even to those possessing particularly sharp eyesight, it is forbidden for consumption.

Specks or Bugs?

Shut Shevet Halevi (7:122) makes an important qualification of the sight-dependent prohibition. He writes that if the naked eye can discern a speck, yet is unable to identify the speck as a bug, there is no transgression in its consumption.

This was the reason why Rav Shlomo Zalman Auerbach (quoted in Shemiras Shabbos Kehilchasah Vol. 1, Chap. 3, Note 105) originally maintained that there was no prohibition in eating the black dots-scales often found on peels of citrus fruit. After he heard that the Chazon Ish prohibited the scales, because before they are covered by their protective shells some motion can be discerned even by the naked eye, he retracted his statement and agreed that they may not be eaten.

One should therefore be careful to clean the fruit and one’s hands of such scales before eating the fruit.

Levels of Obligation in Checking Food

One of the most basic questions in the halachos of bugs is the obligation to check for them. When is the obligation of checking for bugs incumbent, and when does the obligation not apply?

There are three distinct halachic categories of food that define the obligation of checking for bugs.

  1. Mi’ut she’eino matzui: Some fruit and produce are only rarely infested, and for such foods there is no obligation to check them for bugs. This category includes apples, bananas, cucumbers and others. Due to the very small incidence of infestation, there is no obligation to check for bugs.
  2. Muchzak Nagu’a: For some foods, such as lettuce and cabbage (certainly during the summer months), and similar leafy vegetables, a person must assume that the food is infested with bugs, and the food is thus forbidden for consumption unless it is properly checked. If a person fails to check cabbage, and the cabbage is later mixed into a salad and can no longer be checked, the salad would be prohibited to eat.
  3. Mi’ut hamatzui: This is a ‘middle level,’ on which the majority of samples are not infested, but a ‘substantial minority’ is infested. Examples of this are apricots and dates, and many types of fruit, vegetables, beans, and grains, for which the majority of specimens are clean of bugs, but a substantial minority is infested. Foods that belong to this category must be checked for bugs. However, if a person fails to check them, and they can no longer be checked, they are not prohibited for consumption (Shulchan Aruch, Yoreh De’ah 84:9).

If a sample of the food remains, for instance if flour is kneaded into a dough before checking but some of the flour remains in the bag, one should sift the remaining flour. If bugs are found, this proves that the flour was infested, and bread baked from its dough would be forbidden.

How is a Mi’ut Hamatzui Measured?

Because many foods fall into the classification of mi’ut hamatzui, the definition of this criterion carries much weight and has been discussed at length by numerous poskim.

The Rivash (191) adopts a lenient approach to the matter, writing that a mi’ut hamatzui implies an infestation rate of nearly half. According to this, whenever the occurrence of bugs in a food is significantly less than 50%, there would not be any obligation to check the food.

Most authorities, however, cite the ruling of Mishkenos Yaakov (17), who writes that a mi’ut hamatzui is defined by an occurrence of one tenth. This means that even if only one in ten food items will be infested, we are obligated to check each item of food.

After writing at length to defer the ruling of the Mishkenos Yaakov, Rav Shmuel Wosner (Shevet Halevi 4:81, 5:156) writes that the category of mi’ut hamatzui does not require an incidence rate of 10%, and even a smaller rate obligates checking. The condition for this obligation is that the bugs present are accepted as a natural phenomenon, meaning that the clean majority is always accompanied by an infested minority. If the infestation is not inherent to nature, but rather depends on human processing, even an incidence rate above 10% would not obligate checking.[1]

A different definition for mi’ut hamatzui is given by Rav Pesach Eliyahu Falk (Madrich Lebedikas Tola’im, Notes, p. 10, no. 30), one of the world experts on insect infestation and its halachos. In his opinion, the definition of mi’ut hamatzui is a rate of incidence whereby finding a bug would not come as a great surprise. According to this view, the percentage comprising a mi’ut hamatzui would be far smaller than 10%. Although the incidence rate in apricots and dates is probably less than ten percent, we are not surprised to find a maggot or other insect in them, and there is therefore an obligation to check them for bugs.

The common custom to sift flour and to check rice, beans and similar foods for bugs, despite their relatively low rates of infestation, would be in line with this approach.

In conclusion, it is worth returning to the importance of checking foods thoroughly for bugs. As Peri Chadash writes (end of 84):

The Torah is particularly stringent in this matter, including several prohibitions, because this transgression is very common and can occur in most foods, so that one cannot avoid it without investing great diligence. Therefore, the Torah urges us to be wary in this matter with numerous prohibitions. Thus, every person should take great care to avoid this prohibition and even to speak in public of the matter, so that others should also take the required precautions.

The laws of forbidden foods give a dimension of holiness to the act of eating, raising it beyond its status as a simple, physical act, and infusing it with spiritual content. Bugs of all sorts are the lowest levels of life; they are detestable and despicable in their very essence, and the Torah thus forbids their consumption in the harshest terms.

A great responsibility rests on the shoulders of those who are involved in preparation of foods, and it is important to update oneself in the incidence and prevalence of bugs and the ways in which food must be checked and certified as bug-free.

[1] This definition can be questioned from a number of instances in which we find the concept of mi’ut hamatzu in matters that cannot be defined as natural phenomena.  See, for instance, Tosafos (Niddah 44b), who discuss the concept of mi’ut hamatzui in connection with somebody being saved from drowning.

Join the Conversation


  1. I heard that there is a booklet (in English) that was written by Rav P.E. Falk concerning bugs in food. Do you know where I can get it? Is it available on-line?

    1. Unfortunately, I don’t know how to get hold of this booklet. I have friends who have an old version, but the matter of bugs requires constant updating, and depends (as Rav Falk writes) on the particular conditions of the time and place involved (also, general conditions have improved vastly over the years). It is therefore important to ensure that you find an updated version.

  2. I have 2 questions:
    1) The writer quoted the DT before who said particularly sharp eyesight is required.
    The shulchan aruch says when evaluating the transfer of taste from one thing to another, we base it on the taste of an ordinary person, not an expert. Why distinguish here?

    1. If a person has regular eyesight, he can rely on his own checking. There is no obligation to bring the food to somebody with exceptionally sharp eyesight.
      The delicate point, however, is that sometimes a person will miss something, even though he can actually see it, and will find it after somebody with sharper eyesight points it out.
      Best wishes.

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