Death of Pandu in the Mahabharata is the result of a curse. Sage Kindama cursed King Pandu that he would die if he ever touches a woman. The sage cursed Pandu because he had killed an antelope while he was mating with a doe. The antelope was Sage Kindama and the doe was his wife.
Pandu felt that, as he could not now father a child he was unfit to be a king and decided to live in the forest. His wives Kunti and Madri insisted on staying with him in the forest.
Kunti in her teenage due to her service to Sage Durvasa had got a boon that she will be able to summon a god and have children in him. Pandu asked her to make use of the boon and beget children. Thus the Pandavas were born.
Pandu lived happily in the forest with his two wives and five sons in the forest.
But one day he happened to see Madri returning after taking bath. He could not resist the beauty of Madri and touched her. Immediately the curse of Kindama was realized and he died.