Oily food, some contaminated food,does it. It is very impt. you take care and aviod oil and have glucose and rice and light food,if you are in India,please take ayurvedic medicine for it.. Donot exert yourself,iron is also very impt. in this,it is basically,less iron in body that gives rise to it.. Please have pure water,take buttermilk,which means no butter at all,take ample liquids and eat pormegrante.. Do take glucose tablets.. And please consult a physician and an ayurvedic master and in hanumanji 's temple they heal you.. If you in India may be you will understand whaT i am talking about better.. God Bless.