Rahu ketu dosh describes the negative effects of the lunar nodes, Rahu and Ketu, in a person's horoscope. Rahu and Ketu are shadow planets that cause eclipses and are considered malefic in Vedic astrology. They represent the head and tail of a celestial serpent, respectively. Rahu ketu dosh is said to cause various problems, such as delays, obstacles, diseases, conflicts, or misfortunes, depending on the houses and signs they occupy in the birth chart. Some remedies for rahu ketu dosh include performing puja, wearing gemstones, donating to charity, or chanting mantras.