The Prophet (pbuh) said:” Neither vomiting, nor emission, nor cupping breaks the fast.” (Abu Dawud, Book 13, Number 2370)
There are certain things that break a person’s fast, the most obvious being those things that are explicitly forbidden during fasting, i.e. eating, drinking, sexual relations and during menstruation, for females. However, if one eats something forgetfully, then this fast does not have to be made up:
The Prophet said, “If somebody eats something forgetfully while he is fasting, then he should complete his fast, for Allah has made him eat and drink.” (Sahih Bukhari, Volume 3, Book 31, Number 154)
In terms of applying medicine, there is nothing which prevents us from using such as long as it is not entered through the mouth or nose:
The Prophet (pbuh) said, “I have a complaint in my eyes, so may I apply collyrium while I am fasting?” He replied, “Yes.” (Tirmidhi Hadith 2010)
A certain degree of affection is allowed between spouses as this Hadith shows:
‘A’isha reported, “The Prophet (pbuh) used to kiss me while observing fast and who among you can control his desire as the Prophet (pbuh) could control his desire.” (Sahih Muslim, Book 006, Number 2438)
However, the Prophet (pbuh) did report the following Hadith:
A man asked the Prophet (pbuh) whether one who was fasting could embrace (his wife) and he gave him permission; but when another man came to him, and asked him, he forbade him. The one to whom he gave permission was an old man and the one whom he forbade was a youth. (Abu Dawud, Book 13, Number 2381)
WHAT A SICK MAN DOES WHEN FASTING
There are some situations when a person can break their fast.
“If a man succumbs to an illness which makes fasting very difficult for him and exhausts him and wears him out, he can break his fast. (Muwatta, Book 18, Number 18.15.41)
FASTING WHILST TRAVELLING
Hamza bin ‘Amr Al-Aslami asked the Prophet, “Should I fast while travelling?” The Prophet replied, “You may fast if you wish, and you may not fast if you wish.” (Sahih Bukhari, Volume 3, Book 31, Number 164)
Fasting whilst travelling is optional, so there is no sin on the one who chooses not to fast whilst on a journey if they feel that it will weaken them. Allah (SWT) has allowed man not to fast, whilst travelling because He knows that his slaves may not be able to cope.
Anas reported “We were with the Prophet (pbuh) on a journey. Some of us had been observing the fast and some of us had not been fasting. We got down at a place on a hot day. Most of us had the cloth for shelter. There were also those amongst us who sheltered themselves against the rays of the sun with the help of their hands. The observers of the fast fell down (on account of weakness). Those who had not observed it got up and pitched tents and watered the mounts. Thereupon the Prophet (pbuh) said “The breakers of the fast have taken away the reward today”. (Sahih Muslim, Book 006, Number 2484)