If rhododendron is ingested, its toxins confuse, low blood pressure, and possibly death. This is due to a chemical called grayanotoxins. It’s said this chemical is a natural deterrent against insects, however, it also has harmful effects on humans. It’s referred to as “mad honey” because the Romans in the first century B.C.E. were allegedly poisoned with its honey. After they were poisoned, they were so confused they lost their battles. Typically, poisoning occurs when ingesting large amounts of the plant (Royal Botanic Gardens).