Both DS1 and 2 were off school for a week and both were "ill" for only about 24 hours, about 24 hours after the first crop of spots. They itched most of the week but that was it.
Rhus Tox pillules, something by "New Era" for childrne's sckin ailments, piriton, calpol and Nurofen syrup. Tea tree & lavender oils and sodium bicarb in the bath. Calamine lotion is cr*p, get a creamy one. Eurax cream was good for itching (but is for over 2s I think - OK for DS1 tho)