The hidden menace of lupin flour

Dr Harry Morrow Brown looks at this dangerous food a reaction to which could be fatal. For more articles on the many manifestations of allergy, check Dr Morrow Brown's own site at

Julie is aged fifty, her mother and grandmother have asthma, and she knew from bitter experience that eating crab (but not prawns or fish) caused her severe urticaria, and oranges caused swelling of lips and mouth. She also reacted to cats and dogs, but not her own, and from touching Christmas trees, and she was aware that she had been milk intolerant in infancy.

Dramatic reaction

Thus she was a very allergic person from a very allergic family, but she successfully avoided her known allergies until last summer when she ate an Asda own brand Apple Flan at a barbecue. Her mouth reacted immediately with itching and swelling, followed by sneezing, wheezing, urticaria, colic, diarrhoea and fainting. In Accident & Emergency she recovered after intramuscular adrenaline, no cause was identified, and she was prescribed two Epipen adrenaline syringes.

When seen at an Allergy and Immunology Centre no cause was found and she was informed that she was a case of ‘Idiopathic Anaphylaxis’. Blood was not taken for immunological tests, and a negative skin test for Birch pollen excluded the Oral Allergy Syndrome, which consists of symptoms in the mouth and lips on eating certain fruits.

Repeat reactions

Some months later she ate fish and chips, which she knew she could eat, but this time she took mushy peas as well. Within minutes she developed severe colic and anaphylaxis which responded slowly to an Epipen injection and again required treatment at Accident & Emergency.

A few months later, when her son refused to eat his 'onion rings', she ate one off his plate and immediately had another mild reaction, which subsided with an antihistamine tablet.

As she was a practice manager in a nurse led medical practice she knew that foods could cause anaphylaxis, so she became very anxious indeed to find the cause of these frightening episodes, and demanded a second opinion.

Tracking down the cause

Very wisely she had kept the labels from the apple flan from France, the onion rings from Holland, and the mushy peas from England, and brought them with her to the consultation. It was clear that lupin flour was an ingredient of both the flan and the onion rings, while mushy peas contained nothing else whatsoever.

Lupin flour has been reported to cause anaphylaxis in Europe, but a test solution was not available. Being early May a lupin bud was obtained from the garden and squeezed to produce a tiny drop of juice. Pricking through the juice with a prick test needle produced an itchy wheal half an inch across, and pricking through a fresh squashed pea caused an even bigger reaction. Skin prick tests for cat and dog were also positive, but peanut was repeatedly negative and she stated that she could eat peanut with impunity. This is fortunate because two out of three lupin flour allergics in France have been reported to react to peanuts too.

Confirming lupin

Lupin flour was subsequently obtained and a special 5% w/v extract made for prick skin testing. This extract produced skin reactions which developed slowly, were about half the size of the reaction caused by the lupin juice, and died down quite quickly. Placing a little flour on the skin, mixing it with a drop of water, and then pricking through it and wiping it off caused intense itching within a few seconds, and produced a much larger reaction than the special extract. This reaction persisted for two days, being raised and so itchy that she had to take antihistamines.

This dramatic effect showed just how potent an allergen lupin flour can be, even when it is only a minor ingredient of the flan mix. Immunological blood tests were carried out on this occasion, reporting a +++ positive RAST test to lupin, pea, soya, crab, and cat. Since avoiding all members of the pea family, including soya, she has had no more attacks of anaphylaxis. She has also had none of the unexplained episodes of abdominal pain and diarrhoea which had plagued her several times a month for at least ten years, probably a gut reaction to legumes as she was actually very fond of peas and beans. Why she should suddenly have a dangerous reaction to peas is a mystery.

Lupin and anaphylaxis

She is probably the first case of lupin causing dangerous anaphylaxis in this country. Another case has already been found who nearly died after eating a tart imported from Italy, so it is most important that this new menace should become more widely known, especially in people from very allergic families. Similar reports have recently come from Norway and Australia.

In November new laws come into force in Europe requiring food manufacturers to list 12 foods which are have the potential to cause allergies. Lupin was rejected even though it was suggested for inclusion two years ago by the UK-based Institute of Food Science and Technology. The list is gluten, fish, crustaceans, eggs, peanuts, soya, milk and dairy products, nuts, celery, mustard, sesame, and sulphites. Peanut is by far the commonest cause of anaphylaxis, but as French investigators have found that two out of three are also allergic to lupin flour, these patients should be aware of this hidden menace which could cause attacks even when peanuts are being strictly avoided. It would seem advisable to skin test all peanut allergics with lupin as well as peanut in order to identify those at risk..

A case report regarding this new and dangerous allergy was published in ‘The Lancet’ on 9th April 2005, following repeated rejection of the article by the British Medical Journal, which is read by most doctors in the UK, as 'not of sufficient interest to our readers'.

(Since this article was published, lupin has been added to the list of allergenic foods which food manufacturers must declare on labelling - Ed.)

First published in 2007; updated July 2013.

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