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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Thursday 1st December 2011 

Someone kindly emailed to tell me about her experiences with Ruta graveolens, rue. As my correspondent found out, the wrong combination of circumstances can make rue a really unpleasant plant.

It is in the same category as Heracleum mantegazzianum, giant hogweed, that is it produces furocoumarins that can cause burns on the skin. There are ways of looking at Ruta graveolens that make it more of a problem than giant hogweed. This is the result of its unpredictability.

Ruta graveolens, rue

Ruta graveolens, rue

I have brushed my hands through rue repeatedly and suffered no ill effects and, in spite the incident mentioned on the plant page, I am still inclined to the view that the plant has to be cut or bruised to release the furocoumarins.

The woman who emailed me, today, said that she had been working in the garden on a particularly hot and sunny day and she believes it was the combination of the strong sunlight and the open pores resulting from perspiring that led to severe burns. She described ‘spectacularly huge and weepy blisters’ and said that some took weeks to heal and that the back of her hand is still discoloured.

Back in June 15th, I wrote about how little we really know about the plants around us when I discussed the possible reasons for giant hogweed being so dependably dangerous whereas other furocoumarin producers are much more unpredictable. I’m inclined to think that a plant that you know to be harmful is less of a problem than one which is harmful only sometimes. You know to avoid the former but you don’t know when to avoid the latter.

More generally, it does seem that people prefer certainty over doubt. Take, for example, Atropa belladonna, deadly nightshade. It is often said that three berries is fatal to small children. Yet, there are reports of actual poisonings where young children have ingested substantially more than three berries and survived.

Atropa belladonna, deadly nightshade

Atropa belladonna, deadly nightshade

I suppose you could argue over whether a 9-year old counts as ‘small’ child but there is a case where a boy of that age ate between 20 and 25 belladonna berries and survived. Of course, he was fortunate to receive prompt and effective medical treatment and there is no way of knowing what the outcome would have been had that not been the case.

But, that does introduce the sort of caveats that most people seem to want to ignore. It is patently untrue to say that three berries will kill a small child. You need to make that ‘could’ rather than ‘will’ and then you need to introduce conditions based on size of the child, size of the berries, whether or not help is at hand, and so on.

I won’t say too much, today, because I may want to return to the matter in more detail but there was news of a study showing huge variations in the caffeine content of coffee shop coffee. But, the advice on safe use of caffeine, for everyone not just pregnant women, is based on number of cups without any consideration of just what ‘one cup of coffee’ really means.

It’s just like the ludicrous advice to eat five portions of fruit and veg a day. What on earth is five portions?


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