Funny thing about a strong base & a strong acid, when you put them together you get a powerful reaction which can be somewhat explosive - so that’s the implied fifth panel. But then they neutralise each other and you get a fairly inert salt.

The thing that makes them highly reactive - and thus toxic - is their affinity for ionic bonds. But once those bonds form, that same affinity makes the salt stable and safe. Ammonium chloride is used in cough medicine.