Acts That are Permissible During the Fast

(1) Pouring water over one's self and submerging one's self in water

Abu Bakr ibn 'Abdurrahman reported from a number of companions that they had seen Allah's Messenger pour water over his head while he was fasting due to thirst or extreme heat. [Ahmad, Malik and Abu Dawud; Sahih]. Al-Hasan al-Basri said: "There is no harm in rinsing the mouth and cooling ones body with cold water when fasting". Similarly, one can have a bath or swim without invalidating his fast.

(2) Applying Kohl(*) or eye-drop or anything to the eyes

It is the Sunnah of the Messenger of Allah (S) to apply Kohl to his eyes (unfortunately this practice has been abandoned by Muslim men of this age). There are reports of many Sahaba applying Kohl while fasting, among them Anas who did not see any harm in use of Kohl for the fasting person. [Bukhari].
Similar is wearing or smelling perfumes.
(*)A black substance applied to the rims of the eyelids

(3) Kissing and foreplay for one who has the ability to control himself

`Aishah (R) said :" The Prophet (S) would kiss and embrace [his wives] while he was fasting, for he had the most control of all of you over his desires" [Bukhari and Muslim]
Aisha said, "Allah's Apostle used to kiss some of his wives while he was fasting," and then she smiled. [Bukhari]
Zainab (daughter of Ummu Salama) reported that her mother said, "While I was (lying) with Allah's Messenger underneath a woolen sheet, I got the menstruation, and then slipped away and put on the clothes (which I used to wear) in menses. He asked, "What is the matter? Did you get your menses?" I replied in the affirmative and then entered underneath that woolen sheet. I and Allah's Messenger used to take a bath from one water pot and he used to kiss me while he was fasting." [Bukhari]
Umar asked the Messenger of Allah (peace_be_upon_him): Should one observing fast kiss (his wife)? The Messenger of Allah (S) said to him: Ask her (Ummu Salamah). She informed him that the Messenger of Allah (S) did that, whereupon he said: Messenger of Allah, Allah pardoned you all your sins, the previous and the later ones. Upon this the Messenger of Allah (S) said: By Allah, I am the most God-conscious among you and I fear Him most among you. [Muslim]
This is permissible even if it led to some pre-seminal fluid secretions. Jabir said: "The person who gets discharge after casting a look (on his wife) should complete his fast." [Bukhari].
However, young men or women are discouraged to kiss or have foreplay as it may lead to loss of control.
Abdullah Ibn `Amr Ibn al-`Aas said: "We were with the Prophet (S) when a youth came and said: 'May I kiss [my wife] while I am fasting?' He (the Prophet (S)) said: 'No'. Then an old man came and said: 'May I kiss [my wife] while I am fasting?' He said: 'Yes'. So we began looking at one another, so Allah's Messenger (S) said: 'The old man is able to control himself'. [Ahmad; Hasan]

(4) Injections, eye and ear drops

Medically required injections, eye and ear drops and medications placed on wounds, as long as they are not for nourishing purposes they do not invalidate the fast even if one finds a taste in the throat as Ibn Taymiyyah and Ibn al-Qayyim observed.

(5) Cupping (Hijaamah) and blood-letting [or donation] for medical purposes

This used to be an act that breaks the fast. The Prophet (S) said "The cupper [al-Hajim] and the cupped [al-Mahjoum] have broken the fast" [Sahih al-Jami`]. However, this was abrogated later as the The Prophet (S) did it while fasting.
Ibn Abbas said: "The Prophet was cupped while he was in the state of Ihram, and also while he was observing a fast." [Bukhari]
Anas Ibn Malik was asked whether they disliked the cupping for a fasting person. He replied in the negative and said, "Only if it causes weakness." [Bukhari]
Vivisection follows the same ruling as cupping as well as nose or throat bleeding, or bleeding caused by pulling a tooth.

(6) Rinsing the mouth and nose

These acts are allowed in general, but it is disliked to exaggerate (that is, use a lot of water and put the water deep into the mouth or nose while fasting).
Laqit Ibn Sabra reported that the Prophet said: "Exaggerate when rinsing your nose unless you are fasting." [an-Nasa'i, Abu Dawud, at-Tirmidhi and Ibn Majah; Sahih].

(7) Those things which one could not protect one's self from

Such as swallowing one's saliva [or sputum], the dust of the road, sifting flour and so on are all overlooked: Ibn 'Abbas ruling is that: "There is no problem with tasting liquid food or something you wish to purchase." Similarly one can taste food (when cooking) with the tongue without swallowing.

(8) The fasting person can eat, drink, and have sexual intercourse until fajr

If someone has food in his mouth when fajr is beginning, he should spit it out. If he is having intercourse (with his wife) at that time, he should immediately stop. If he does so, his fast will still be valid. If he continues in these actions at that time, he will have broken his fast. Al-Bukhari and Muslim record from Aishah that the Prophet said: "Bilal makes the call to prayer while it is still night; therefore, eat and drink until Ibn Umm Maktum makes the call to prayer."

(9) It is permissible for the fasting person to be Junub (sexually defiled or having had intercourse or a wet dream) at the time of Fajr (that is, a person is not required to perform ghusl before fajr)

Umm Salamah [the wife of the Prophet (S)] narrated that AbuBakr ibn AbdurRahman reported that Marwan sent him to Umm Salamah to ask whether a person should observe fast who is in a state of junaba and the dawn breaks upon him, whereupon she said that the Messenger of Allah (S) (was at times) junub on account of intercourse and not due to sexual dream, and the dawn broke upon him, but he neither broke the fast nor recompensed. [Muslim]

(10) Delaying the purifying ghusl (bath) from menstruation till after fajr (dawn)

If the blood of a menstruating woman or of a woman with post-childbirth bleeding stops during the night, she can delay ghusl until Fajr.

(11) Involuntary actions

Involuntary actions such as ejaculation in a wet dream or involuntary vomiting do not invalidate the fast [the case of vomiting has already been indicated in the hadith concerning intentional vomiting].