My buds may my ears sweaty and itchy. I don't use them due to this.
I have been to an audiologist who confirmed that the buds aren't "breathable", so for people like myself with narrow ear canals, after a period of time (sometimes as short as 10 minutes), there will be a build of of sweat and heat through lack of "ventilation, which in turn will cause the discomfort.
If this is left untreated, this can give long term issues as the fine skin lining will continue to be "sensitive ", causing itching, flaking and weeping.