The basic rule about forbidden food is that whatever is unclean, unwholesome or harmful must not be eaten. All substance and alcohol are also forbidden such as poison and narcotics.

What is specifically forbidden to eat

The basic rule about forbidden food is that whatever is unclean, unwholesome or harmful must not be eaten. These may be summarized as follows: 

1. There are 10 forbidden types of food mentioned in Allah’s book.

• ‘Carrion’ refers to any animal that dies without being properly slaughtered. This is forbidden because as its blood is not spilled, it is likely to be harmful to eat. However, when there is no other food available, and one is about to die out of starvation, small quantities may be eaten only to sustain life. Excluded are fish and locusts, which can be eaten without the requirement of being slaughtered. 
• ‘Blood’ refers to spilled blood, as Allah says in another verse:

The blood left over in the flesh and the veins after slaughter is permissible, as this is impossible to fully drain. Also, it is excludes what is specifically mentioned as permissible, such as the liver and the spleen.
• The ‘flesh of swine’ is forbidden. Allah has combined all these three in the verse that says:

• That which has been dedicated to other than Allah’ refers to the flesh of any animal slaughtered in the name of anyone other than Allah, because this implies associating partners with Allah. The slaughter of animals for food is an act of worship, and it cannot be addressed to anyone other than Allah. He says:

• The ‘animal that has been strangled’, is forbidden to eat whether through natural causes or deliberately. (by suffocation).
• ‘Or by a violent blow (beaten to death)’, by a staff or a hammer or some heavy article.
• ‘Or killed by a fall’, from a high place and dies.
• ‘Or gored to death’ by another animal and dies.
• ‘Or those from which a wild animal has eaten (savaged by a beast of prey,),’ such as a lion, tiger, wolf, dog, etc. The beast may eat a part of it and leave the remainder. 
However, in each of the last five cases, if the animal is caught before it dies and is slaughtered properly, it thus becomes lawful to eat, as Allah says in the same verse: ‘except that which you may have slaughtered when it is still alive.’
• ‘And those which are sacrificed on idolatrousstone altars’. These refer to the altars that were erected around the Ka'bah where animals were sacrificed in pre-Islamic days. Again, this is an idolatrous act, and therefore, it is forbidden to eat the animals slaughtered on these altars.  Needless to say, this is a general statement and it applies to all animals slaughtered on altars, statues or other structures that are associated with worship of any kind. Such slaughtered animals are unlawful to eat.
2. Also forbidden is all food and drink that is harmful, such as poison, wine and all intoxicants and narcotic drugs. Allah says:

3. It is forbidden to eat any part cut from a living animal, as the Prophet (peace be upon him) says:

4. Predators, such as lions, tigers, leopards, wolves, etc. Abu Thalabah reports that

  The Prophet (peace be upon him) said:

5. Birds which catch their prey with their claws, such as eagles, falcons, kites and owls. Ibn Abbas reports:

6. Scavenger birds such as vultures, ravens and crows, because they feed on what is unwholesome.
7. Any animal we are recommended to kill, such as snakes, scorpions, mice and kite. A’ishah reports that the Prophet (peace be upon him) said:

8. Domestic donkeys. Jabir reports:

9. What is disgusting to eat, such as mice, snakes, wasps and bees. Allah says:

10. Any animal that feeds mostly on impurities, whether it be a camel, an ox, a sheep, chicken, or any other. However, if the animal is confined and given wholesome food for several days until it becomes clean, then it becomes permissible to eat. Ibn 'Umar reported:

  Ibn 'Umar used to confine such animals for three days before slaughtering, but other scholars say that they should be confined for longer.