Parshas Shemini highlights a prohibition that is of special relevance to one of the mitzvos of Seder Night: the prohibition of eating bugs and the concomitant obligation to check foods before eating them. This is especially pertinent to the Romaine lettuce we use for Maror, but is also highly relevant the year round.

As we will mention below, the Gemara writes that there is a great virtue in refraining from eating insects, and even states that it is sufficient to justify the entire redemption from Egypt! The issue of insect infestation is relevant to many different foods that we regularly consume, and it has gotten worse in the modern era for various reasons.

In the article below we will seek to understand the details of the prohibition and to set out guidelines for checking foods for bugs. Why is this prohibition so severe? Which foods much be checked before they are eaten? What must be done when foods cannot be checked? And should we worry about specks on fruit? These questions, among others, are discussed below.

The Severity of the Prohibition

Among the many laws of kashrus elucidated in Parashas Shemini, the Torah notes the prohibition of eating insects (Vayikra 11:41): “Every swarming thing that swarms upon the earth is detestable; it shall not be eaten.”

The Pasuk explains 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.”  Thus, worms, spiders, centipedes, flies of all sorts, and so on, are all included in the prohibition.

The Torah concludes this chapter by stressing the gravity of this prohibition, which brings spiritual defilement upon the person who transgresses it (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 in connection with this prohibition, the Gemara (Bava Metzia 61b) derives that the prohibition against eating bugs is sufficient justification for 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 things.

Note that while one who consumes the meat of a non-kosher animal transgresses a single Torah prohibition, one who consumes an insect transgresses four, five, or six Torah transgressions – the precise number depending on the type of insect and the number of times the Torah repeats its prohibition (see Makos 16b, and Aruch Hashulchan, Yoreh De’ah 84:13-14). This underscores the severity of the matter.

Although most are included in the definition, it is noteworthy that not all individual creatures we commonly refer to as “insects” are 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, even though the same kind of insect that has walked on land is prohibited.

This halachah is the source of the controversy that erupted some years ago over Anisakis worms in the flesh of fish, the debate centering on whether or not the worms leave their place of origin. In a modern context, it also raises the question of scientific knowledge appearing to contradict Talmudic statements, in this case, that fruit flies are formed in the fruit itself .

We will limit the discussion in this article to the basic issues concerning the prohibition against eating insects, and the duty to check foods for bugs.

Levels of Obligation in Checking Food

Among the most basic questions in the halachos of insects is the obligation to check foods for them. When is there an obligation to check for bugs, and when does the obligation not apply?

There are three halachic categories of prevalence that determine the obligation to check 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, pears, bananas, cucumbers, and others. Due to the very small incidence of infestation, there is no obligation to check them for bugs.
  2. Muchzak Nagu’a: Some foods, such as regular lettuce and cabbage (during the summer months) and similar leafy vegetables, are assumed to be infested with bugs based on experience, and the food is thus forbidden for consumption unless properly checked. If a person fails to check cabbage, and the cabbage is later mixed into a salad (without being ground—see below for more details) and can no longer be checked, the salad may not be consumed.
  3. Mi’ut hamatzui: This is an intermediary level: most samples of the food are not infested, but a substantial minority is infested. Examples of this are (in general) apricots and dates, and many types of fruit, vegetables, beans, and grains for which most specimens are clean of bugs, but a substantial minority are 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, the resultant mixture is 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 without 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 is forbidden for consumption.

How is Mi’ut Hamatzui Measured?

Because many foods fall into the classification of mi’ut hamatzui, the definition of this category 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 view, whenever the occurrence of bugs in a food is significantly less than 50%, there is no obligation to check the food.

Many 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 of a specific kind is generally infested, we are obligated to check each of those food items.

After writing at length to reject 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. According to Rav Wosner the condition for a mi’ut hamatzui is that bugs are accepted as a natural phenomenon, meaning that the clean majority is usually accompanied by a naturally infested minority.

However, this position does not seem to be broadly accepted by other contemporary authorities.

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 can be smaller than 10%. Although the incidence rate in (good quality) apricots and dates far less than ten percent, we are not surprised to find a maggot or other insect in the fruit, and there is therefore an obligation to check them for bugs.

The common custom in Israel to sift flour, and to check rice, beans, and similar foods for bugs, despite their relatively low rates of infestation, is in line with this approach. However, in many climates and locations finding a bug in rice or flour is in fact a great surprise, so that there would not be an obligation to sift and check even based on this stringent approach.

Annulments in Mixtures

We don’t always have an opportunity to check foods for bugs. For instance, when eating outside the home, we are not able to check food for bugs, and need to rely on others. This is also true for foods that we buy in stores. For instance, if we buy strawberry juice in a local store, we can generally assume that the strawberries were not properly checked for bugs. When are such foods permitted for consumption, and when must we refrain from eating foods that were not properly checked?

Concerning bugs, it is important to note that by contrast with other non-kosher foods, a whole bug is not annulled even as a small minority (less than sixty to one) in a mixture with other foods. This is because a whole bug has the status of a beriah—an entire creature—which is not nullified even in one thousand times their own volume. Therefore, if a whole insect falls into a pot of kosher food, and gets lost therein, the entire pot of food is prohibited for consumption (Shulchan Aruch, Yoreh De’ah 100:1).

If a gnat falls into a pot of potatoes (and gets lost), the only way to permit the potatoes for consumption is by ensuring (by cleaning off each potato) that the gnat is not present in the food one eats. 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).

The fact that a whole bug is considered a beriah also implies that one transgresses the full Torah prohibition even when eating less than a kezayis (by contrast with other forbidden foods; Makkos 16b; Rambam, Laws of Forbidden Foods 2:24). As the Aruch Hashulchan (Yoreh De’ah 84:12) 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.”

Annulment of Chopped Bugs

The principles outlined above apply to whole bugs, but not to bugs that are not whole. 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. 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 is forbidden to intentionally cause a prohibited food to become annulled, and the laws of annulment may only be relied on post factum. Based on this principle, it seems that one should have to ascertain that the wheat is completely insect-free prior to grinding, for otherwise one causes their annulment intentionally.

The Terumas Hadeshen (siman 171) responds to this question by stating that grinding unchecked wheat is permitted due to a combination of factors. 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 that even when the first factor is not relevant one can rely on the second factor).

Yet, the 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. The Pischei Teshuvah (Yoreh De’ah 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 (though he mentions that other authorities dispute this point).

Checking wheat before grinding is of course a substantial trouble, and therefore it is permitted to grind the wheat into flour without checking it before for bugs.

Checking at Home before Grinding

The above leniency will likewise apply to other instances of mass production.

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

In domestic settings, however, the trouble involved in checking and cleaning is usually not substantial, and under most circumstances there is thus an obligation to check and clean food rather than just chopping or grinding it. Yet, for foods that are especially difficult to check, and which need to be ground in any case, it is permitted to grind the food after ensuring that there is no definite infestation (by means of superficial cleaning and inspection).

Poskim rule further that where a food is extremely difficult to check one may take steps to minimize the possibility of any bugs remaining, and then grind up the food, even where the 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. Even if bugs remain after the washing, they are nullified in the mixture with the chopped parsley. 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; the sefer is available on our site at

Of course, using bug-free products provides an easier solution to the problem.

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 average human capabilities. Authorities derive from this principle that the prohibition against consuming bugs does not apply to those insects that are not visible to the naked eye.

The Binas Adam (34) actually quotes from Sefer Ha-Bris that it is forbidden to consume vinegar, because scientists discovered that vinegar is full of  bugs that can be seen through a magnifying glass. In a similar vein, the She’elas Yaavatz (2:124) writes that if a bug is detectable by means of a magnifying glass, the food is prohibited.

Yet, based on the foregoing principle the Binas Adam rejects this opinion, writing that eating bugs invisible to the naked eye involves no transgression. This ruling is the clear consensus of later poskim (see Aruch Hashulchan 84:36; Machazeh Eliyahu 91), and the Maharshak (Tuv Taam Va-Daas, Tinyana, K.A. 53) writes that there is no need to use devices beyond the naked eye in determining the kashrus of foods.

Rav Moshe Feinstein (Iggros Moshe, Yoreh De’ah 2:46 and briefly in 4:2) adds that one cannot suggest that it is obligatory to check with a magnifying glass (or microscope), because this will imply that previous generations (which lacked the tools to check) transgressed the prohibition of eating forbidden foods – which is surely false.

Yet, it is important to clarify that the leniency of eating invisible bugs applies only to bugs that are truly invisible to the naked eye. If a bug can be seen by holding it up against the sun, or against a dark or bright background, or when in motion, then the fact that the bug is camouflaged in its environment (for example, a greenfly on a lettuce leaf) does not permit its consumption.

This principle is stated by the Bach (84) concerning bugs that can only be seen by holding something up to the sun, and reiterated by Shut 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. The Machazeh Eliyahu therefore recommends using a magnifying glass for checking lettuce, thereby ensuring that all visible bugs are indeed spotted.

Moreover, not all eyes are identical, and some people’s eyesight is stronger than others. The Chasam Sofer (Orach Chaim 132) writes that even bugs that cannot be discerned by those possessing “weak vision” are prohibited (the matter depends on average eyesight), and it is therefore important to ensure that food is checked by somebody with good eyesight. In fact, the Darkei Teshuvah (84:15) goes so far as to state that a bug is forbidden for consumption unless invisible even to those possessing particularly sharp eyesight, though this opinion does not seem to be supported by most poskim.

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. Because no motion of the specks can be seen, there can be no prohibition. Yet, Rav Shlomo Zalman later heard that the Chazon Ish prohibited the scales because some motion can be discerned by the naked eye before they are covered by their protective shells, and he therefore retracted his statement and agreed that they may not be eaten.

Rav Chaim Kanievsky (cited in Nezer HaChaim, p. 375) explains the opinion of the Chazon Ish in a different light: Although no movement can be discerned, the visibility of the black speck is sufficient to render its consumption prohibited. An earlier similar discussion can be found in the Darkei Teshuvah (84:28).

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


In conclusion, it is worth returning to the importance of checking foods thoroughly for bugs. As the 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.”

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.

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