Poison

Poisons, toxins, and venoms are all poisonous, intoxicating substances - powders, liquids, and gases - that can be used by ninja in combat. Poisons come with a variety of effects, ranging from body weakness, paralysis, or death.

Canon Types
There are different types of poison, some more effective than others:
 * Tsunade has been noted by Jiraiya to be the only person capable of poisoning a ninja without them knowing, as she managed to spike his sake with an odourless, colourless poison that left him unable to properly control his chakra.
 * Kabuto Yakushi has developed a poison which is specifically designed to suppress the Wood Release kekkei genkai.
 * Sasori had developed such a poison that even if a small amount is introduced into the bloodstream, the affected person will die within three days while also being painfully paralysed for the duration. According to Sakura, this poison is refined with heavy metals which gets into the muscles and destroys the cells. The antidote for this poison is extremely complex - so much so that no one in Sunagakure was capable of creating it.
 * Orochimaru's true form's blood is poisonous, and evaporates upon contact with air, paralysing anyone who breathes it in. Its potency is such that even Sasuke Uchiha, who has gained an immunity to most poison, was affected.
 * One of the poisons taught to Sakura by Shizune is able to be entrenched in kunai and has a delayed effect, as Naruto was cut with it but collapsed some time afterwards.
 * Sakura also uses smoke bombs that contain a strong knock-out gas that can even render ninja like Sai, Lee, and Kiba unconscious in moments.
 * Hanzō, in his youth, transplanted the poison sac of a black salamander in his village. He was able to poison the environment just from breathing. He also imbued his kusarigama's blade with poison.
 * Ino Yamanaka has been shown to at least have knowledge of poisonous plants seen early when she threw poisonous plants into Ami's mouth. She also makes heavy use of wolf's bane in the video games.

There are animal which can produce different types of poisons:
 * Snakes summoned by Orochimaru, sometimes are able to secrete venom from their fangs.
 * Ibuse can release a large amount of Poison Mist that almost instantly paralyses anyone that breathes it in.

There are also several species of insects that use poison in their attacks. While other insects, such as the kikaichū, can be cultivated for the purpose of neutralising poisons and toxins used on the bug-user's allies:
 * Rinkaichū - Torune Aburame and Shikuro Aburame can subsequently infect the opponent with these bugs, causing an excruciatingly painful and likely fatal injury, unless the afflicted area is swiftly removed. However, there is in fact an antidote, but only Shikuro Aburame knows how to make such an antidote.
 * Kochū - Used by Yōji Aburame, these insects can infect targets with a poison that will paralyse the victim and kill them shortly afterwards. As the poison disappears upon death, it can't be found during autopsies, making these insects perfect for assassinations, as they are imperceptible as mosquitoes yet as deadly as scorpions.

Non-Canon Types

 * Aniki, the leader of the Moya Triad, had tried several types of poison against Kakashi, which were to make him hiccup, laugh, and cry uncontrollably until he died from it.
 * Bees - The Kamizuru clan of Iwagakure has ninja bees that can inject venom into a enemy through their stingers.
 * The Wandering Ninja Clan used an odourless type of poison powder that slows down the victims' senses and reaction time.
 * Fuen used a poison that is thin and tiny enough to be taken into the air, and cause those who inhale it to see whatever she wants.
 * The Sea Route of Silence Gang used the Moulding Mushroom to poison their victims and make them easy prey.

Usage
Most poison users use poison on their weapons through various means. Sakura, for example, after learning from Shizune coats her kunai with poison so that if she is able to cut the target, they are instantly injected with the toxic substance. Puppet-users, such as Kankurō and Sasori, prefer to put poison inside their puppets so that they inject via hidden bladed weapons. Sasori, similarly to Sakura, puts poison that is clearly noticeable on the blades of his puppet, the Third Kazekage, as well as in his Iron Sand, which is far less noticeable.

Poison may be used in other forms, not only as a liquid substance. It can be used in a mist form, as demonstrated by Shizune, with her Poison Mist technique. Inhaling the slightest bit of poison can prove fatal, as seen when Sasori trapped Sakura in two consecutive waves of his poison mist. Such vapours can also be used for paralysing effects, as Ibuse demonstrated.

Combating Poisons
Certain characters have encountered poisons throughout their careers as ninja. Those skilled in the fields of chemistry and biology are capable of producing antidotes to the poisons. Tsunade, during the Second Shinobi World War, was able to produce antidotes to every one of Chiyo's poisons, much to the latter's resentment. During the mission to rescue Gaara, Sakura Haruno demonstrated the skill to not only extract and analyse Sasori's poison swiftly, but also produced an antidote to counter it, something Chiyo could not do.

Apart from using antidotes to poisons, a ninja can also work to build-up a tolerance to certain poisons by gradually exposing oneself to non-lethal amounts of those poisons. Orochimaru, in the effort to make Sasuke Uchiha into the perfect vessel for his Living Corpse Reincarnation technique, made it a point to make Sasuke immune to most poisons, such as the one that Shizune taught to Sakura Haruno in order to use on her kunai. Anko was seemingly put under the same regime during her time with Orochimaru. Mifune has been shown to have built up an immunity to both Hanzō and Ibuse's poison.

Real Life Versions of Naruto Poisons
Although many of these poisons are completely fictional, a handful of them are (or could have been) influenced by a real-life poison. A few of these are explored below:
 * There are many toxic heavy metals, such as cadmium, manganese, lead and mercury, but only a few can cause the symptoms caused by Sasori's poison. An example of a heavy metal that can cause muscular dystrophy (or destruction), is lead. Chronic lead poisoning can lead to gastrointestinal, neurological and neuromuscular symptoms. Lead can cause neuromuscular symptoms through a few different routes: 1) by interfering with DNA transcription of enzymes that help in the synthesis of vitamin D, 2) reducing red blood cells in the body, and 3) by entering the brain and affecting neurochemical balances. For Sasori's poison, a large concentration of lead would be necessary, but if it were mixed with other heavy metals, it is not unreasonable to believe that such a poison could exist.
 * Although Hanzō gets his ability from transplanted poison sacs of a black salamander, the reality is black salamanders are not poisonous. However, other types of salamanders are. One example is the fire salamander. The toxin that these salamanders can secrete is called Samandarin. Similar to Hanzō's poison, samandarin can enter the body through skin exposure or oral ingestion. Another similarity is that both poisons are very lethal. Enough samandarin exposure can result in death via respiratory paralysis.
 * Ino's wolf's bane is one of the oldest documented poisons. Wolf's bane is a type of plant, and the actual poison (aconitine) is extracted from this plant. When aconitine is in the body, it binds to sodium-ion channels on skeletal muscles (i.e. biceps, thighs, etc) and cardiac muscles (i.e. the heart). This keeps the muscles depolarized, or "on", and can lead to symptoms that include, but are not limited to: increased heart rate, numbness, chest pain, and hyperventilation.

Trivia

 * Tsunade likened the Wind Release: Rasenshuriken to poison due to the cellular damage it inflicts on the user if used at melee range, potentially leading the user to be crippled as backlash.