Sun in the first house is in its own house. Sun is more or less at home in the first house. According to B. V. Raman, Sun in first house gives a strong moral character, right-minded nature, ambition and love for power. The native is cheerful and very optimistic. Also he/she is quite popular.

     Sun along with Saturn, Mars or Ketu in first house gives burns or scars. Gentle planet like Moon, Mercury and Jupiter in first house as co-tenants of Sun may strengthen the character of the native. Sun in debilitated state in first house could lead to skin problems and blood impurities. There are chances of frequent fevers, inflamations and eye infections.

     Generally Sun in first house does good. It gives prominent eyes and fantastic vision. It gives confidence which sometimes borders on arrogance. Strength and character to defeat enemies as well as bad timings is also a boon of Sun in first house. There are very few health concerns and most of the times native remains healthy by mind and body. Things like depression and other mental ailments are unlikely especially if Sun is free from influence.

     Normally Sun in first house is a blessing to have. But if Sun is combust or in a bad sign than there are chances of health, skin and eye problems. In these cases the natives should eat food rich in Vitamin A and Vitamin C like carrots, oranges, tamarind, amla(Gooseberry), butter and other sources. Native should regularly recite the gayatri mantra which gives good health and well-being. Last but not least twelve steps of surya namaskar keep skin and digestion problems away and keeps the body and health in check. 

References:

Raman, Bangalore Venkata. How to Judge a Horoscope. Delhi: Motilal Banarsidass, 2014. Print.