okasan,
Barely water is good enough for baby to ease heaty in e body especially when bb has constipation. However, you must buy china barely which is "warm"; enough for bb.
Since you are allergy to si shen, maybe you can feed your bb with brown rice and a bit of si shen powder (buy fr medical hall) to test whether yr bb allergy to it or not.
Hmm, if you start with plain rice cereal, bb wont want to eat brown rice cereal due to the texture. Plain type is smoother than brown. Like for us, we get used to eat white rice, we oso find hard to eat brown rice. My nephew is started with brown rice when he was baby till now.
twinkle-starry,
You can buy si shen powder from medical hall. Si shen is mean to help bb to have more appetite to eat more food / milk. Also help in digestion. Mostly, added into those ready made brown rice cereal or brown rice powder. You have to check with medical hall or e sinseh the amount of si shen powder add into your cereals (off shelves). Too much, might cause bb to get hungry faster or if bb is allergy might will diarrohea.