Rhododendron Poison – Truth behind the science of Sherlock Holmes

Written by: Captain Skellett // December 27th, 2009 // How Things Work, Poisons, Science in the Movies

I saw Sherlock Holmes last night with SexyMan, the cinema was packed and we sat in the second row from the front. I watched the movie like a fan watches a tennis match, but surprisingly it was still good!

It might have helped that any great expectations had been dashed by a friend on facebook, but nonetheless I thought it was an enjoyable, action-packed, fast-paced fast-talking very sexy flick.

But then I’m not a film critic. I am, however, a science geek. This post has been carefully written to avoid spoilers, but if you want to play it safe go and see the movie and come back in 3 hours. K?

At one point in the movie they talk about rhododendron poison, but don’t explain at all what it is.

Rhododendrons (and azaleas, the dwarf (midget) version) are a moderately toxic group of plants. If you’re out strolling the mountains near the eastern side of the Black Sea in Turkey, or generally in the USA or UK, then don’t eat this plant:

Rhododendron ponticum.

Not all members of the genus are poisonous, but play it on the safe side and don’t eat random plants.

It’s not HUGELY poisonous, about 100 grams need to be ingested by a 25 kg child to seriously poison them, but it is a problem for livestock – particularly sheep, goats and cows – who munch on the flowers and get seriously sick.

Of course, if you boiled it down and concentrated the liquid… well that’s a different story. The toxin is water soluble, so it can be extracted from the leaves and flowers.

The toxin is called grayanotoxin. It binds to specific sodium ion channels in cell membranes (which I’ve talked about before) and prevents inactivation, causing persistent activation of muscle and nerve cells. This causes a range of symptoms based on where the activated cells are located, such as muscle weakness, vomiting, sweating, salivation, seizures, and either dangerously slow or dangerously fast heartbeat, depending on the dose. In the end, it can cause death.

Don’t think you’re safe just because you don’t make a habit of eating plants – the toxin is also found in the nectar of flowers, and bees that feast on them can make “mad honey.” It took out an army in 401 BC lead by Xenophon of Athens against Persia – hundreds of soldiers vomiting and unable to walk for a day. No-one died, unlike in 67 BC, where the army of Mithradates IV killed Pompey the Great’s soldiers while they were incapacitated. It’s biological warfare, victory has never tasted sweeter.

Mad honey is still a problem today – not so much the stuff in a grocery store (which is diluted and problem tested and stuff) but organic honey direct from the beehive can be risky. Plus some men use it as an aphrodisiac. Idiots.

That’s the rhododendron poison, making a comeback after 2400 years on a big screen near you! What did you think of the movie? There were lots of sciencey deductions made that weren’t very well explained, so if you have any questions, post a comment and I’ll do me best!

Captain Skellett

I be Captain Skellett. Me blog started in April 2009 when I was working full time and didn’t get a chance to talk science. Now I have changed jobs and talk science all the time, but that doesn’t stop me blogging. More About Captain Skellett   Google


11 Responses to “Rhododendron Poison – Truth behind the science of Sherlock Holmes”

  1. jack li says:

    omg, this is exactly what i needed. can u tell me specficially which part of the movie it came from? thks so much!

    Captain Skellett Reply:

    Sry jack li, been thinking and thinking and can’t for the life of me remember… I can see leaves steeping in a bowl, but it’s been a few weeks since I saw the movie. I’ll open this question to the floor – anyone remember?

  2. jack li says:

    its all good. i finally found it. its in the very last scene. thks tho!

  3. Aya says:

    Hey, so in the movie, how comes blackwood when he used that poison, he didn’t have all these other symptoms of ‘vomiting, sweating and so’ and just had ‘no pulse’. I just don’t understand the mechanism of takin a poison, stayin totally alive but only having asystole.

    They may have taken some artistic license, methinks.

  4. Karan says:

    Sir, but u said slow pulse right , it is not possible that there is no pulse, or is it? Lord Blackwood the gr8.. hehe sorry..

  5. samik chatterjee says:

    but what about the NO PULSE EFFECT…….did not get that part right………the hanging stuff was brilliant though…….

  6. Angela B says:

    It made me think of the ‘distilled liquor’ given to Juliet by Friar Lawrence in ‘Romeo and Juliet’. It created much the same effect, didn’t it? They thought she was dead, and actually put her in the family crypt.

  7. daremo again says:

    Let us remember the times in which this took place. People would die if they bit their tongue from infection. In winter, streets would rise 3 to 6 feet from animal and human waste/fecal matter. Medical understanding was at best barbaric. Doctors feeling for a pulse had was not a science and a lot was taken for granted. Today a medic specifically feels for a pulse with the pointer and middle, never reaching over the neck and for the wrist careful not to wrap the diagnosing hand around. (the thumb tends to be more insensitive and carries a bit of pulse itself). Def the movie took some creative license, because distillation processes were not very good. much was unknown. why were the rich called blue bloods…well they drank from the finest leaded cups and glasses. the term ‘mad as a hatter’ comes from the ill affects of mercury used to make felt for hat construction. ‘Sleep tight’ what does that mean!! Well, in the day before our metal springs, ropes were strung to the bed frame to hold the straw mattress. the ropes were tightened to give better support and thus better sleep; as for the bugs, well, you were sleeping on straw/grass. Therefore, sleep tight and do not let the bed bugs bite! This movie was just okay at making people understanding how we lived just 100 years ago. watch ‘dirty cities’ to get the full blow of it. As for you Captain Skellett, cheers and all the best! Why is the rum gone!! oh, that’s why!

  8. Noun says:

    This is great. Exactly the answer I was looking for. And it’s in the part where Holmes enters the home of the midget scientist. Great movie. Great explanation behind the venom that supposedly made the evil dude feel dead. Cheers.

  9. siva prasad says:

    i would like to know the scientific reason behind lord black wood’s pretension of no pulse and hanging

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