Sometimes I'm a little confused why this is a tag in general (; ̄Д ̄)?
For a while it was so often naturally found alongside Onions that the tags became near-synonymous (users would post things like "saw ice cream and was waiting for the onions on page 8" or "tagged Onions but no ice cream???". But some vocal people would subscribe to Onions and then complain any time the doujin ended up more Ice cream-heavy or for whatever reason didn't enjoy the combination, so Ice cream got its own tag.