Is it allowed to touch the body and to kiss the wife during fast? What are the differences among sperm, pre-seminal fluid and Wadi?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad  is His slave and Messenger.

The following shows the difference between Maniyy (sperm), Mathy (pre-seminal fluid) and Wady:

Maniyy: it is a thick white fluid emitted by the male or female as the result of sexual ejaculation. Some scholars define Maniyy as the thick spurting water discharge through orgasm. When the above characteristics are not present Ghusl (a ritual bath) is not compulsory for ritual purity. Another case where Ghusl is not compulsory is when the sperm is discharged due to illness or extreme cold or the like. It is narrated in a Prophetic Hadeeth that Ghusl is only obligatory if one discharges (sperm) with orgasm. However, if sperm discharge happens unwillingly and without pleasure, then one does not have to perform Ghusl.

If someone wakes up and finds some sperm moistness on him or on his clothes he should perform Ghusl.  This also applies to women. The Maniyy of a woman is a thin yellow fluid. Ghusl is obligatory any time one has sexual intercourse.

According to the predominant opinion of the Muslim scholars  Maniyy is a pure fluid.

Mathy: it is a thin white sticky fluid which is discharged due to sexual stimulation, e.g. thinking about sexual acts, or kissing or the like. One is usually unaware of exactly when it is discharged. It emits from both the male and female. Muslim scholars unanimously agree that Mathy is impure.

Wady: it is a thick white fluid that comes after urinating. It is also considered impure. Ibn 'Abbaas,   said: "Maniyy discharge requires Ghusl. However, Mathy and Wady only require performing Wudhoo' (ablution) and cleaning the private parts and part of the clothes it touched".

For information on kissing and the like, please refer to Fatwa: 81596.

Allaah knows best.