Question: May Allah be good to you for this blessed advice Oh Virtuous Shaikh. Is it correct that a lot of Coffee is disliked?
Answer: Coffee is from the permissible drinks, however, if it is said that a lot from it harms, then it becoms haram. Next, the people differ in this. So this man which it is said to him not to drink coffee because it is harmful to you, we say to him: do not drink it because it is haram upon you. As for another man who is used to drinking it and is not affected by it, we say to him: drink how much you want.
Like this, there is no one who doubts that dates are halal, however, if it is said to a man who is afflicted with diabetes, do not eat dates because it will affect you and harm you. We say: dates are haram upon you although they are halal . So something halal from food or drink or clothing if it includes harm upon a person, then it becomes haram upon. Just as when something haram can deflect a necessity it becomes halal. So a hungry man who fears upon himself death, it is halal for him to eat dead meat and pork and it is halal for him what is slaughtered upon an altar.
The one who is forced out of necessity to wear silk, a mean by that a man, then it is allowed for him to wear silk if he has [skin ] allergies and the doctors say that which will remove it is wearing silk. We say: wear silk although it is haram, however it necessity it is allowed for him to wear.
So what is important is that something can be haram for one person and halal for another and that is in accordance to what his condition requires. As for what is absolutely haram, then it haram upon everyone. However, along with that prohibition upon everyone, if a person is forced to it out of necessity and his necessity will be deflected by using it, it then becomes halal.
[Taken from http://www.ibnothaimeen.com/all/noor/article_3668.shtml]
Faisal Ibn Abdul Qaadir Ibn Hassan