Thank you for your query.
usually last upto 5 days but can last longer.
Give your child lots of fluids.Avoid milk,juices and wheat products.
Give him some antispasmodic drops for pain.
Give him paracetamol
Consult your doctor for tests if the child worsens.
If you have any further queries you are free to consult me.
Hope this answers your query.
Wishing a speedy recovery.
Have a nice day.