Well in our family, if there were any motions, we did this:
1. Boil some water (a glass/cup amt) and let it cool down to get to warm/lukewarm temperature.
2. Take small pinch of salt and mix it in the water.
3. Add quarter tea spoons of sugar and mix with the water. You have to saturate the water with the sugar. So after adding every time the sugar, stir the water well and again add. Do this process till you see the first time a SMALL clump of crystallized sugar (at the bottom of the glass, etc) that no longer mixes with the water even after stirring.
At that point, let the person drink it. This solidifies the stool and lessens the urge to go to bathroom again and again.
Every time the person goes to bathroom, let them drink that afterwards. Soon, it should stop. Also, it's better to make fresh new glass every time the person drinks than making large amt of it and drinking in interval. If not a fresh glass, it lessens the impact on the immune system I think.
Also, people can die of diarrhea (usually from the fatigue) so if it continues for more than 4-6 times, take the person to the doctor.
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more info about causes of diarrhea is here:
Diarrhea
I think its high time you take the child to the doctor now. So take him asap.