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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Monday 20th August 2012

Writing a substantial number of blog entries, especially about a limited subject range, is bound to result in repetitions from time to time. Richard Herring, whose excellent daily blog has run for over ten years, has absolutely no restriction on subject but recognises that there are times when he’s writing something very similar to one or more of his previous pieces.

It is no surprise, therefore, that I’ve written about Paracelsus before. You can’t write about the vagaries of what constitutes a poisonous plant without taking account of his pronouncements on the topic.

On 7th January, I wrote;

'Paracelsus, a Swiss doctor and philosopher from the early 16th century is frequently quoted on the subject of poisons. There are a number of ways of presenting Paracelsus’s core point about poisons but this comes from Arthur Edward Waite’s late 19th century translation;

'‘[Other animals and fruits] are not in themselves either food or poisons, but, as regards themselves, and inasmuch as they are creatures, they share their perfection equally with us. When they are taken by us as food they are thus poison to us. Thus a thing becomes poison to us which in itself is by no means a poison.’

'That last sentence is the key to his ideas and it gets rendered as everything from ‘poison is in everything, and no thing is without poison’ to ‘one man’s meat is another man’s poison’.

'What Paracelsus’s words have come to mean, though I’m not sure it is what he meant, is that there is no necessary reason for a plant to be poisonous to us and you cannot be absolute about what is and is not a poison.'

What set me thinking about Paracelsus concerns a plant substance I’ve written about before Thursday 24th November; capsaicin from plants in the Capsicum genus. The website of a TV station in Arizona reported that a forklift truck pierced a 5 gallon drum of concentrated chilli peppers leading to evacuation of a FedEx facility at Memphis airport. 117 employees were involved with 115 being dealt with at the scene and two requiring hospital admission after suffering chest pains.

Capsaicin is the substance used to make pepper sprays and the drum concerned was, apparently, en route to a pepper spray manufacturer.

Capsicum annuum

Capsicum annuum

I was drafting this piece in my head as I toured the supermarket where there were plenty of fruits from Capsicum annuum and other species of peppers. No-one, of course, was even remotely contemplating the evacuation of the premises because of the presence of a dangerous substance.

When I wrote about the use of pepper sprays, last year, I noted;

‘Though often used in cooking by many cultures, Capsicum annum is categorised by the Horticultural Trades Association (HTA) as Class ‘C’ in its list of potentially harmful plants and, in her book ‘Poisonous Plants – A guide for parents and childcare providers', Liz Dauncey describes some pretty unpleasant symptoms that can arise from ingestion, skin contact or inhalation.’

On that occasion, I didn’t pursue the point about its inclusion in the HTA list. Liz Dauncey notes that ornamental cultivars are not suitable for eating and that may account for its appearance because it is one of only four ‘mainstream’ food plants that appear on the list. By ‘mainstream’ I mean those things that everyone would recognise as food rather than some of the obscure things that some people would claim as edible.

The other plants listed by the HTA are Asparagus, because consumption of the fruits can be harmful except for Asparagus officinalis, the species grown for harvesting of the young tips, Passiflora caerulea, passion fruit, where, like the chilli pepper, ornamental varieties can cause problems and Ficus carica, fig, where contact can result in a phototoxic reaction.

Though not on the HTA list, Dauncey provides information for four other food plants that can be harmful. Solanum tuberosum, potato, is, of course, a close relative of Atropa belladonna, and if the tubers are exposed to light, they produce solanine, one of the main toxins in deadly nightshade.

Rheum x hybridum, rhubarb, has poisonous leaves though the leaf blades make a tasty dessert. Apium graveolens, celery, is, like Pastinica sativa, parsnip, a source of furocoumarins that can cause severe blistering if skin contact is followed by exposure to bright sunlight.


Which takes us back to where we started. The concentration of furocoumarins varies from plant to plant demonstrating, very clearly, that the poison is in the dose.

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