An article in today’s Seattle Times reports that three King County residents were recently affected by foodborne toxins. Unfortunately, one came from a sample of local honey.
According to the article a man became ill after eating a portion of honey he had purchased at a local farmer’s market. He reported vomiting and “intestinal difficulties” which began about an hour after consuming the honey. The honey sample was sent to the state department of agriculture, but tests were unable to confirm the presence of a toxin.
However, the man’s symptoms led officials to believe the honey contained grayanotoxin, a material found in rhododendron plants. The condition, also known as “rhododendron poisoning” or “honey intoxication,” is well-documented but rare.
Grayanotoxin is a naturally-occurring neurotoxin found in the nectar of rhododendrons. According to Wikipedia, symptoms include salivation, perspiration, vomiting, dizziness, and low blood pressure. The condition is rarely fatal and usually abates within 24 hours.
In a cruel hit to small honey producers, the author of the Seattle Times piece writes that local honey is much more likely to contain toxic levels of grayanotoxin than honey coming from large commercial producers because commercial producers mix honeys from many sourcesa variation on “dilution is the solution to pollution.”
The ABC & XYZ of Bee Culture mentions that both the nectar and pollen of rhododendron are poisonous to bees as well as humans. Although the toxin can kill the bees, it is well diluted with water in the nectar. But as the water is driven from the nectar to produce honey, the grayanotoxin is concentrated to poisonous levels.
I didn’t find any references to how frequently honey intoxication occurs but the numbers must be low. The Puget Sound area is overrun with rhododendronsin fact it is the Washington state flowerbut few cases of poisoning are reported. My own property is loaded with both honey bees and rhododendrons but I have never seen a honey bee on a rhododendron flower. These observations lead me to believe that rhododendron is not a preferred forage for honey bees and they probably collect it only in rare circumstances when other more favorable blooms are not available.
If you are interested in foodborne toxins, the Seattle Times article is interesting. Besides honey intoxication you can read about toxic squash syndrome and combroid fish poisoning. So, what’s for dinner?