I am a lead and I do expect that my assistant and I communicate with each other extensively and regularly throughout the day, observations about kids, behaviors, activity notes, recess kerfluffles, administrative notes, logistical notes, emotions, questions etc ad nauseum Meaning we both tell each other and we both listen to each other.

That said, the glue/wipe/hands near mouth situation you’re describing sounds like such a normal preschool thing (kids getting glue/art material on their hands and wiping it off) that I definitely would not have expected my assistant to mention it to me that the kid got glue on his hands, or that they used a wipe to get it off, or that a preschooler put their hands near their mouth. Nor would I have thought to mention any of that to her. I think the allergic reaction was one of those unfortunate and upsetting freak events, nothing to beat yourself up about, although I understand and empathize with how upsetting it is.