How does oral thrush cause newborn to be irritable and not sleep?

Causes pain: In adults, oral thrush can be very painful. So even though little babies can't tell us specifically that they are in pain, we can only assume that it has similar effects on them as it does on adults. For more info on the symptoms of thrush, check out this link from the Mayo Clinic: http://www.mayoclinic.org/diseases-conditions/oral-thrush/basics/symptoms/con-20022381