Are sulfur ointments bad for babies' skin in treating insect bites?

Sulfur ointments are mostly use to treat skin disorders and not insect bites which I don't think is that serious yet. I've seen in this article that sulphur is used for treating a condition called cradle cap among babies: http://www.livestrong.com/article/153742-uses-of-sulphur-ointment/ For precautions, use sulfur only as directed. Do not use it more often and do not use it for a longer period of time than recommended on the label, unless otherwise directed by your doctor.

It depends on the intensity of the sulphur's content in the ointment. If you use an ointment specifically made for baby's skin (usually 5%-10%), it will not be dangerous. In fact, it is one of the most safest options that doctors will prescribe for babies and pregnant women. My friend mixes a tiny bit of Scabisil sulphur ointment with baby lotion for her baby's insect bites and scabies.

You can also try just using a cool washcloth or ice wrapped in cloth to soothe the affected area. Most insect bites don't really get bad unless they're scratched and turn into open wounds.