Rahu in Vedic Astrology rules over your luck, religious beliefs, speculative nature, honesty, old age diseases, past life karma, alchoholism, smoking habit etc.Rahu stays in each sign for about 1.5 years and usually takes 18 years to complete a zodiac cycle. It always travels in retrograde motion and in general, Rahu is benefic if placed in 1st, 3rd, 6th, 11th houses from ascendant.It is also good is placed in Aries, Taurus, Gemini, Leo, Virgo, Sagittarius signs. Rahu in Virgo can give knowledge or education in medicine.Rahu is responsible for Bacterial Diseases and controls all bacteria in our food or body. Here is the proper explanation by our principal astrologer Pt. Rishiraj Tiwari Ji.