how do you know if your child is lactose intolerant?

One way to know is by flatulence and at times stomach pain.

i would say it would aggrivate her stomach more than constipate

It can and will cause a painful tummy and constipate. My son and I both are lactose intollerant... him moreso than me. I switched him to soy milk and he's great with it. No pains no constipation. There are other milks you can try though if you don't want soy... Rice milk & almond milk for example. Just stop the reg. milk if you think that is what is causing the prob. And wait a few days. Let her system calm. You'll know pretty quick if it was the prob. or not. Luck to you!

My DD is lactose intolerant but not horribly. It give her awful diarrhea about 20 min after having it. She doesn't complain about it and lactaid has helped tremendously! Until we decided that was the problem she had an awful time gaining weight form it. I am pretty sure it can be different for everyone though so I would suggest doing what our ped. asked us to do which was remove ALL dairy from the diet for one week. Take note on any changes in you LO bowel pattern then report to the ped.

Try giving her a milk with less fat in it. Whole milk has a lot of fat and that sometimes bothers the stomach. Ask the doc about giving her 2% or 1% milk or buy Deans Lactose Free milk. I am Lactose Intolerant and I get horrible stomach cramps, constipation and sometimes diahrrea.