Islamic ruling on bodily fluids revolves around two points we are going to tackle with:

1. Bodily secretions and their ruling with regard to ghusl and wudu

2. Things that necessitate ghusl.

With regard the first point, we’d like to furnish you with what late Sheikh Sayyed Sabiq stated in his well-known book, Fiqh As-Sunnah:
Wadi: It is a thick white secretion discharged (by some people) after urination. It is considered impure. `A’ishah (may Allah be pleased with her) said, “Wadi comes out after urination. The person should wash the private parts and perform ablution. It is not necessary to perform ghusl.” This is reported by Ibn Al-Mundhir.
Madhi: This is a white sticky fluid that flows from the sexual organs because of thinking about sexual intercourse or foreplay, and so on. The person is usually not aware of when exactly it is secreted. It comes from both the male and the female sexual organs, although the amount from the latter is usually more than the former. Scholars agree that it is impure. If it gets on the body, it is obligatory to wash it off. If it gets on the clothes, it suffices to sprinkle the area with water, as it is very hard to be completely protected from this impurity, especially for the young, single person.
`Ali (may Allah be pleased with him) said: “I used to excrete madhi, so I asked a man to ask the Messenger of Allah (peace and blessings be upon him) about it. I was shy to do so because of my position with respect to his daughter (`Ali was the Prophet’s son-in-law). He (peace and blessings be upon him) said, ‘Make ablution and wash your penis.’” (Reported by Al-Bukhari)
Sahl Ibn Hunayf said, “I used to suffer from excessive amounts of madhi. I used to make lots of ghusl because of it. So, I mentioned this to the Messenger of Allah (peace and blessings be upon him) and he said, ‘It is sufficient to take a handful of water and sprinkle it over your clothes wherever the fluid appears.’” (Reported by Abu Dawud)
Mani (semen): Some scholars say that semen is impure, but apparently it is pure, for it is only recommended to wash it off if it is still wet, and to scratch it off if it is dry. `A’ishah (may Allah be pleased with her) said: “I used to scratch the semen off the Messenger of Allah’s clothes if it was dry, and wash it off if it was still wet.” (Reported by Ad-Daraqutni and Al-Bazzar). It is also related that Ibn `Abbas (may Allah be pleased with him) said: “I asked the Messenger of Allah (peace and blessings be upon him) about semen on clothes. He said, ‘It is the same as mucus and spittle. It is sufficient to rub the area with a rag or cloth.’

As for urine, it only invalidates wudu’ (ablution).

As for things that necessitate ghusl,Sheikh M. S. Al-Munajjid, a prominent Saudi lecturer and author states the following:
“The things that make ghusl a must are:
1. The emission of semen, because the Prophet (peace and blessings be upon him) said: “What requires water (ghusl) is if you see water (i.e., semen) coming out of you.” (Reported by Muslim)
2. Contact between the genitals, because the Prophet (peace and blessings be upon him) said: “If one part enters the other part (in another report: if one
part touches the other part), then ghusl becomes obligatory.”
(Reported by Ahmad and Muslim) This ghusl is obligatory whether or not fluid (semen) is released. “Touching” here refers to the entry of the tip of the penis into the vagina, not mere touching.
3. Menstruation and nifas (post-natal bleeding), because Allah says what means: “. . . And when they have purified themselves, then go in unto them as Allah has ordained for you. . .” (Al-Baqarah: 222); and because the Prophet (peace and blessings be upon him) said to Fatimah bint Hubaysh (may Allah be pleased with her): “When your period starts, stop praying, and when your period ends, perform ghusl then start praying again.” (Reported by Al-Bukhari)
4. Death. The dead—except for a martyr slain in battle—must be washed (ghusl), because when his daughter Zaynab died, the Prophet (peace and blessings be upon him) said: “Wash her with water three or five times, or as many times as you see fit.” (Reported by Al-Bukhari). And when a man who was in a state of ihram (consecration for Hajj or `Umrah) was killed by his riding-beast, he (peace and blessings be upon him) said: “Wash him with water and lotus leaves and wrap him in his two garments, but do not embalm him or cover his head, for he will be raised on the Day of Resurrection pronouncing the Talbiyah.” (Reported by Al-Bukhari)

There are other types of ghusl about which the scholars differed as to whether they are obligatory, such as performing ghusl on Fridays, or whether a person who becomes Muslim needs to perform ghusl upon entering the faith.

There are types of ghusl which are encouraged, such as: ghusl on the two `Eids; ghusl after washing a dead body; ghusl before entering the state of ihram or entering Makkah; ghusl for a woman who is suffering from istihadah (abnormal non-menstrual bleeding) before every Prayer; ghusl after being unconscious; and ghusl after burying a mushrik (one who associates others with Allah).