||The examples and perspective in this article deal primarily with Abrahamic faiths and do not represent a worldwide view of the subject. (December 2012)|
In some religions, an unclean animal is an animal whose consumption or handling is taboo. According to these religions, persons who handle such animals may need to ritually purify themselves to get rid of their uncleanliness.
In Judaism, the concept of "unclean animals", or more accurately "impure animals", plays a prominent role in the Kashrut, the part of Jewish law that specifies which foods are allowed (kosher) or forbidden to Jews. These laws are based upon the Books of Leviticus and Deuteronomy of the Torah and in the extensive body of rabbinical commentaries (the Talmud). The concept of unclean animals is also mentioned in the Book of Genesis, when Noah is instructed to bring into the Ark all sorts "of pure beasts, and of beasts that are impure, and of fowls, and of every thing that creepeth upon the earth".
In the Torah, some animals are explicitly named as pure or impure, while others are classified by anatomical characteristics or other criteria. In some cases, there is some doubt as to the precise meaning of the Biblical Hebrew animal name.
According to Jewish dietary laws, to be "pure" an animal must also be free from certain defects, and must be slaughtered and cleaned according to specific regulations (Shechita). Any product of an impure or improperly slaughtered animal is also non-kosher. Animal gelatin, for example, has been avoided, although recently kosher gelatin (from cows or from fish prepared according to kosher regulations) has become available. (The status of shellac is controversial.) The prohibitions also extend to certain parts of pure animals, such as blood, certain fat tissues, and the sciatic nerves. Finally, it is forbidden to cook milk or dairy product with meat, or even use the same kitchen utensils for both.
Other mammals forbidden by the Torah are "crawling creatures", such as mice, and flying bats. According to the Torah, mammals that both chew their cud (ruminate) and have cloven hooves, such as cattle, goats and sheep, are kosher; while those that have only one of the two characteristics are impure and cannot be consumed. Leviticus cites explicitly the camel, because it ruminates but does not have a cloven hoof; the hyrax and the hare are excluded on the same grounds. It also explicitly declares the pig unclean, because it has cloven hooves but does not ruminate.
According to Leviticus 11:9–10, anything that comes from the water ("in the seas, and in the rivers") that has both fins and scales may be eaten.
The Torah names only a few birds that may not be eaten; those not in the list are presumed to be kosher. However, the precise identity of the unclean birds is a matter of contention in traditional Jewish texts. It is therefore common to eat only birds with a clear tradition of being kosher, such as domestic fowl.
The Torah allows eating certain kinds of "winged swarming things" (i.e. insects) while prohibiting others. However, due to uncertainty about the Hebrew insect names, rabbis today recommend that all insects be considered unclean. An exception is made for certain locusts (Schistocerca gregaria), which are traditionally considered kosher by some Yemenite Jewish communities. Leviticus 11:20–23 details which insects are not to be eaten, and due to the wording all insects are considered impure to avoid mistaken consumption.
Explicit list 
Some scholars, especially secular ones, have conjectured that the Jewish concept of "unclean animals" arose out of public health concerns by community leaders, since, in the conditions of the times, some of those animals are indeed more likely to cause food poisoning or transmit diseases to people who consume them. Other scholars viewed the Levitic prescriptions as somewhat arbitrary handicaps that were established to test the Jews' commitment to God and their community.
British anthropologist Mary Douglas proposed that the "unclean" label had philosophical grounds, namely it was cast on foods that did not seem to fall neatly into any symbolic category. The pig, for example, was seen as an "ambiguous" creature, because it had cloven hoof like cattle, but did not chew cud.
In the very early days of Christianity it was debated if converts ought to follow Jewish customs (including circumcision and dietary laws) or not. According to the account of the Council of Jerusalem in Acts 15, a compromise was reached between those who wanted full compliance and those who favored a more liberal view. It was agreed that the converted Gentiles would have to bear "no greater burden than these necessary things: that ye abstain from meats offered to idols, and from blood, and from things strangled, and from fornication". However the extent and application of this decision has been a matter of some debate (some see a parallel with the Noahide Laws of Genesis 7).
Jesus is quoted in Mark 7:14–23 as saying "There is nothing from without a man, that entering into him can defile him [...] whatsoever thing from without entereth into the man, it cannot defile him; because it entereth not into his heart, but into the belly"; and also in Matthew 15:10–11. "Not that which goeth into the mouth defileth a man; but that which cometh out of the mouth, this defileth a man." These statements are often cited for support of the view that Christianism does not include dietary restrictions.
Supporters of the liberal view also point to Peter's vision reported in Acts 10:10-16 and Acts 11:5-10 in which God invited him to eat "fourfooted beasts of the earth, and wild beasts, and creeping things, and fowls of the air". They also draw support from the writings of apostles Timothy (1 Timothy 4:3–5, "For every creature of God is good, and nothing to be refused, if it be received with thanksgiving; for it is sanctified by the word of God and prayer") and Paul (Colossians 2:8–16}, "Let no man therefore judge you in meat, or in drink, or in respect of an holyday, or of the new moon, or of the sabbath days").
Paul affirms that any created thing in the food line is acceptable as long as it meets two tests -it must be sanctified (or set apart as holy) by the Bible, and it should be prayed over with thanksgiving. Pork has been a particularly disputed topic, since it is explicitly forbidden in the Old Testament, where it is compared to idolatry. There is debate over this text as the New Testament never directly declares pork as holy, but rather God refers to as an abomination and therefore not sanctified.
While the majority of Christians agree that the dietary restriction of the Old Testament were lifted with Christ's New Covenant, there are Torah-submissive Christians who believe that they should still be observed. Supporters of this view may argue, for example, that in the Old testament, Daniel spoke of unclean food and drink as "defiling one's body" Daniel 1:8, and that in the New Testament one's body is said to be the "temple of God", and "If anyone defiles the temple of God, God will destroy him". Some read Jesus's reply to questioning by the Pharisees in Matthew 15:1-2 and Matthew 15:19-20 as implying that his statements about "which goeth into the mouth" (Mark 7:14–23 and Matthew 15:10–11) referred to the question of hand washing, rather than clean and unclean foods.
Others also argue that the dietary restrictions predate Leviticus, and that Paul in Colossians 2 was referring to the ceremonial feast days such as the Feast of Unleavened Bread and not clean and unclean foods. Others argue that the liberal view would imply the acceptance even of alcohol, tobacco, rats and roaches as "clean food"; and that God never declares something an abomination and then changes His mind.
Supporters of the stricter view have also disputed the interpretation of Peter's vison Acts 10:5-10, claiming that God was merely instructing him not to refer to gentiles as "unclean" since salvation had been extended to them.
One modern example of a Torah-submissive group is the Seventh-day Adventist Church whose co-founder Ellen G. White was a proponent of vegetarianism. Many Seventh-day Adventists avoid meat for health reasons, though vegetarianism is not a requirement. Members of the United Church of God as well as other Sabbath-keeping Christian Churches also believe in abstaining from unclean meats.
Roman Catholic traditions 
In the Roman Catholic Church, it was forbidden to eat meat (defined as the flesh of any warm-blooded animal) on Friday, but as a penance to commemorate Christ's death rather than for meats being regarded as "unclean". After the Second Vatican Council, the mandatory Friday abstinence from meat was limited to Lent, although some traditionalist Catholics still maintain the abstinence year-round.
Eastern Orthodoxy 
Seventh-day Adventist 
Since the 1860s when the Seventh-day Adventist Church began, wholeness and health have been an emphasis of the Adventist church. Adventists are known for presenting a "health message" that recommends vegetarianism and expects adherence to the kosher laws in Leviticus 11. Obedience to these laws means abstinence from pork, shellfish, and other foods proscribed as "unclean".
Research funded by the U.S. National Institutes of Health has shown that the average Adventist in California lives 4 to 10 years longer than the average Californian. The research, as cited by the cover story of the November 2005 issue of National Geographic, asserts that Adventists live longer because they maintain a healthy, low-fat vegetarian diet that is rich in nuts and beans, they do not drink alcohol or smoke, and they have a day of rest every week.
In Islam several animals are considered unclean and their consumption is sinful (haraam), except in case of necessity; while others are permitted (halaal), as long as they are slaughtered in the proper manner and with blessings given to God.
The Qur'an expressly forbids consumption of "the flesh of swine" There are no other "impure animals" explicitly named in the Qur'an. If someone converts to Islam, Allah "allows them as lawful what is good and prohibits them from what is bad; he releases them from their heavy burdens and from the yokes that were upon them".
For other animals, great importance is given to the manner of its death: forbidden are blood and carrion ("dead meat"), and any animal that has been "killed by strangling, or by a violent blow, or by a headlong fall, or by being gored to death". Also forbidden is any animal that has been eaten by a wild animal, unless the person is able to slaughter it before it dies.
Finally, the Qur'an forbids food on which has been invoked a name other than Allah, which has been sacrificed on stone altars, or has subjected to the pagan practice of raffling with arrows. Food slaughtered by an idolater is forbidden, but food that is acceptable to Jews and Christians is allowed to Muslims as well.
On the other hand, in Islamic tradition there are many animals that are not considered good for eating, and therefore haraam. These include lions, tigers, eagles, crows, vultures, kites and scorpions. Fish, seafood and locusts are allowed (even if not properly slaughtered), as are camel and rabbit meat.
The dog is mentioned in the Qur'an several times, for instance as a companion of the Dwellers of the Cave. According to the majority of Sunni scholars, dogs can be owned by farmers, hunters, and shepherds, for the purpose of hunting and guarding; the Qur'an states that it is permissible to eat what trained dogs catch. Among the Bedouin, the saluki dogs are cherished as companions and allowed in the tents.
Nevertheless, many Islamic teachers state dogs should be considered unclean and that Muslims licked by them must perform ritual purification. According to a Sunni Islam Hadith, a plate that a dog has used for feeding must be washed seven times, including once with clean sand mixed with the water, before a person may eat from it.
Many Rastafarians believe that pigs are unclean and hold to a diet known as Ital.
Cultural animal taboos 
In many societies there are strong cultural (but non-religious) taboos about eating or having contact with certain animals. For example, in most Western countries there is a strong cultural taboo against eating dog, cat, or monkey meat.
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