Variably severe systemic allergic reactions after consuming foods with unlabelled lupin flour: a case series

Lupin flour allergy can be severe and unpredictable and despite European legislation (Commission Directive 2006/142/EC) introduced in December 2006 it is often still used without disclosure on the list of ingredients in foods such as pastries. There is significant cross-reactivity between lupin and peanut but less so with other legumes [1]. We describe four cases of severe lupin flour allergy in adults with and without associated legume sensitisation. The absence of adequate food labelling and poor public and physician awareness of lupin as a cause of severe allergic reactivity led to a marked delay in the diagnosis and required detailed investigation to uncover the cause of the reactions.

Lupin flour is derived from Lupinus angustifolius and is a legume. Its use, particularly in baked products, has increased significantly over the last decade. This may relate to its high protein content and its possible ability to lower cholesterol levels and improve glycaemic control [2]. The major allergenic proteins of lupin are not fully characterised but include α- and β-conglutins, with a lesser presence of γ- and δ-conglutins [3]. The β-conglutin corresponding to Lup an 1, which is considered the major lupin allergen [2], has sequence similarities to the peanut Ara h 1 [3]. Of interest, however, specific IgE to Ara h 1 was negative in patients one and two. The mechanism of lupin sensitisation in our patients without any legume or peanut sensitivity is unclear. However, the recent introduction of lupin flour in foods may represent a novel protein and thus reactivity may represent a new allergy for the patient.

Sensitisation to lupin flour is significantly more frequent than clinical reactivity [4, 5]. In both children and adults, lupin sensitisation is more frequent in those with peanut allergy (17.1% and 14.6% respectively) and those with underlying atopy (2.5% and 3.7% respectively) [5]. Others have reported significantly higher rates of sensitisation in those with peanut allergy [6, 7]. In our practice we have found lupin sensitisation in approximately one-fifth of our patients with peanut allergy and with only a few having mild and localised clinical reactivity. Clearly this creates problems on how to advise patients. We suggest that lupin-sensitised patients without evidence of any sort of previous reactivity continue on a normal diet but if eating out or consuming unfamiliar foods they should have antihistamines available. With the development of even mild oral itching with lupin contaminated foods, then this should be avoided completely. These patients may benefit from a double-blind oral lupin challenge if there is doubt about clinical reactivity.

In regard to our four cases of lupin allergy, our second patient had a mildly positive SPT to peanut and with positive specific to peanut and to the Ara h 2 and Ara h 8 proteins but not to the Ara h 1 or Ara h 3. This appears to suggest a coincidental nut allergy and a possible underlying OAS. The negative results to Ara h 1 makes cross-reactivity with the lupin Lup an 1 protein very unlikely. In addition, the absence of specific IgE to Ara h 3 makes the peanut sensitivity unlikely to be due to a legume-based cross-reactivity. However, our fourth patient had positive specific IgE to fenugreek, chickpeas and lentil and evidence of a mild clinical legume allergy.

The amount of lupin flour that can elicit a discernable reaction varies considerably and may be as low as 0.5mg [7]. In adults working with lupin flour, sensitisation and clinical reactivity has been reported to cause rhinitis, asthma and conjunctival irritation [8]. Lupin allergy in adults can be very severe and often without previous atopy [9]. Indeed in our first patient without concurrent atopy even the skin testing produced symptoms in the throat and later vomiting. The frequency of lupin allergy in adults with an underlying OAS is not known but was evident clinically in the third patient and suggested serologically on blood tests with the second patient.

In comparison to the European Continent, lupin is a rarely used ingredient in the United Kingdom. When used it is often a minority (<10%) ingredient often in conjunction with wheat flour. The reactions in all our patients occurred after the consumption of wheat products that were later discovered to contain lupin flour. Knowledge about lupin allergy is poor even though 8% of those with peanut allergy may have a potential lupin allergy.

Our first patient demonstrated lupin flour-induced anaphylaxis without prior atopy. This was first reported in children by Wassenberg and Hofer in 2007 [10]. Among the 1522 patients with suspected food allergy reported by Hieta et al. [9], 25 (1.6%) were SPT positive for lupin and seven of these patients manifested varying degrees of clinical reactivity. Our second case had two significant allergic reactions of unknown cause before lupin allergy was diagnosed. In the fourth case, three to four reactions had occurred annually for 7 years before lupin allergy was diagnosed. It is therefore important that testing for lupin sensitivity is undertaken in all patients presenting with severe allergic reactions without obvious cause. As with the case reported by Rossi et al. [11], the reaction in our third case involved lupin flour used in a gluten-free product. It is vitally important therefore that: a) clinicians are aware of lupin flour as a potential allergen, b) the general public are further educated as to the usage of lupin flour particularly in baked goods and the particular risk posed to those who have a peanut and legume allergy, and c) that manufacturers ensure that any amount of lupin flour (even if masked by wheat flour) is included on lists of ingredients such that affected individuals can take necessary steps to minimise their risk.

Lupin allergy without previous atopy or legume sensitivity can present for the first time in adult life and vary in severity from asymptomatic sensitisation to severe anaphylaxis. The more expensive high-end wheat-based foods are most frequently incriminated in allergic reactions. Skin prick testing and analysis of specific IgE can readily confirm lupin allergy and a high index of suspicion should be maintained because lupin is frequently used without being listed in the ingredients. In highly sensitised individuals, even skin testing can cause symptoms. Legislation to enforce the declaration of lupin as an ingredient and improved medical awareness of lupin as a cause of serious allergic reactions is suggested.

Written informed consent was obtained from the patients for publication of this manuscript and accompanying images. A copy of the written consents is available for review by the Editor-in-Chief of this journal.