1)Before Knowing effect of Rahu In 1st house we have to know about Rahu and Tanu Bhav so you may read this
Tanu Bhav Base Of Your Horoscop—
2)So Rahu in 1st house generally effects our body constitutions, health, brain, nature and behavior.
3)Rahu is a shadow planet so there is no definite physique in classical. Only mentions Rahu is just like Saturn and Rahu behave like sign lord where it is placed. So if we consider Rahu is same as Saturn then native may has unfair in colour and tall in heights ( Strongly recommended please consider rashi for better outcome).
4)Rahu is natural malefic so Rahu in 1st house may cause ill health. Rahu is a planet which shows hidden quality and 1st house belongs to upper body limbs (Head) so native may suffering hidden problem of upper body limbs. So it is seen native may suffering many disease such as way one is cure then other may attack on native and native may wandering one doctor to another doctors.
5)1st house belongs to brain and nature so Rahu in 1st house, native may be suffering from phycological problem. Some time Rahu In 1st may also give skin related problem.
6)Rahu in 1st house may also cause mouth and dental problem.
7)Rahu is planet of Maya creation or imagination so Rahu in 1st house may also cause hysteria type problem.
8)Rahu is tamsic planet so Rahu in 1st house is giving tamsic brain.
9)Rahu is a planet which have accelerating power and insight seeing capacity so Rahu in 1st house is increasing native’s brain power. So native may has great imagination power and guess hidden matter . So native may be smart from nature and a great copying quality .
10) Rahu in 1st house is indicating native may be fickle in nature so they are just change their behaviour according to situation.
11)Native may be false speaker but they speak such a way then nobody guess theirs false.
12)Rahu is planet which give attachment regarding materialistic world. So Rahu in 1st house make native money minded person. So they may be wealthy.
13)Rahu is belong to hiddness, hype creator, explosiveness type temper So when Rahu occupy 1st house then native have such type nature.
14)Rahu is planet which belongs to Maya so Rahu in 1st house native may has inclinations regarding Magician or mysteries activity or Jadu Tona.
15)1st house is tanu bhav so 1st house Rahu gives native to extreme mental capacity just like unguided missile when any other planet may guided Rahu then native may do any impossible work or get name or fame.