PLease think twice if you are weaning baby for this reason. What if you later on found that the baby is allergic to cow's milk & soymilk? What are you going to give him?
I would suggest you to watch your own diet (taught by a paediatrician). Start from only having least allergenic food (pork, banana, choi sum, carrot, and plain rice) for 3-5 days, see if the baby's condition's improved. If it is, then add one more food into your diet, and continue having for 3 days. In this way, you maybe able to find out what your baby's allergic to. That's what i did and my baby's allergic to egg and nuts.
Having said that, some baby's allergic to dusts, dustmites, fragrance, wool, carpet so avoid contacts to these might be helpful too.