It may be due to an allergic reaction
. You should take regular anti allergics and also give them to the child. You should have complete examination by a Dermatologist
to avoid spread to the other ones at home.
Take regular medicine such as Cetrizine
and apply scabion lotion all over the body below the neck to yourself and child after bath every day.
Change clothes every day and wear soft clothes.
I hope I am sucessful in solving your query If u have further you can ask me
Get well soon
Dr. Azhar Sattar