Curate, connect, and discover
Cuddle pollen, but with Danny being affected in his ghost form, he wants to be under someone else's skin, AKA overshadow someone. Which. Of course, it has a lot of awful implications. But the pollen is getting so bad, he's beginning to wonder if overshadowing would be worth it.
His human form is getting hives while he's being afflicted by the pollen. So. He tries being creative. Overshadow a stray cat, a pidgeon, even a rat, but no dice. Animals don't seem to cut it.
Finally, he cannot take anymore of this, and he overshadows the first human being he sees. This is, of course, The Bat.
(Late additions:
Imagine if Bruce's will is enough to keep his wits about it. So now he's got a ghost kid inside his own body and he's clumsy because he's constantly fighting for control.
Danny does petty commentary at the most inopportune moments, like a little devil on the Bat's shoulder.
Bruce is completely livid at Constantine and Zatara's sudden unavailability, so he's stuck until the ghost goes away on his own.)