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Keywords:

  • food allergy;
  • Parietaria;
  • pistachio nut;
  • respiratory allergy

Pistachio nuts (the anacardiaceous species Pistacia vera) are widely used in the catering industry to produce ice creams, cakes, and mortadella; they are also eaten roasted. Very few cases of pistachio nut sensitization have been reported (1, 2), whereas sensitization to other dried fruits is well established. We previously described two patients, sensitized to Parietaria allergens, who were affected by severe oral allergy syndrome after the ingestion of pistachio nut (3). Using SDS–PAGE and immunoblotting techniques, we also found a slight degree of cross-reactivity between Parietaria and pistachio nut allergens in these two cases (3).

This study aimed to evaluate the frequency of allergic sensitization to pistachio nut in atopic and nonatopic individuals, and to determine whether sensitization to pistachio nut is more frequent in patients with Parietaria pollinosis.

A total of 1529 subjects, who were examined at our allergy center from 1 February 1996 to 31 January 1998 for nasal and/or bronchial symptoms that seemed to be IgE-mediated, were enrolled in the study. Exactly 564 individuals were monosensitized to Parietaria allergens, and 490 to other allergens (e.g., house-dust mites, Gramineae, and animal dander). The remaining 475 were nonallergic. Patients underwent anamnestic data collection, physical examination, and cutaneous and serologic diagnostic tests. Skin prick tests (SPT) were administered according to a standardized method with commercially available allergenic extracts for the common inhalant allergens and the most frequently offending foodstuffs such as hazelnut, peanut, walnut, and pistachio nut (Lofarma Laboratories, Milan, Italy). Only patients with a positive SPT to pistachio nut underwent the prick-prick test (PPT), administered, according to Dreborg & Foucard (4), with fresh foods (pistachio nut and other Anacardiaceae foods, i.e., cashew nut and mango). Wheal areas (expressed as mm2) were measured after SPT and after PPT. Total and specific IgE was measured in serum samples from patients SPT-positive to pistachio nut (Sferikit, System Lofarma Laboratories, Milan, Italy).

Of the 1529 atopic and nonatopic individuals enrolled in the study, 11 (0.72%) were SPT-positive to pistachio nut (Table 1). All 11 patients were from the Parietaria-sensitized group. No evidence of cutaneous or serologic sensitization to pistachio nut was detected in patients allergic to other allergens or in SPT-negative subjects. Finally, no patient sensitized to both Parietaria and pistachio nut had a positive SPT to other dried fruits and/or other anacardiaceous nuts. All patients who were SPT-positive to both Parietaria and pistachio nut had ingested moderate or low quantities of roasted pistachio nuts or of food containing pistachio nut (ice cream, cake, and mortadella). No subjects of this study frequently consumed large amounts of pistachio nut.

Table 1.  Results of diagnostic procedures in patients sensitized to both Parietaria and pistachio nut*
      In vivo tests (wheal areas as mm2) In vitro tests
   After exposure to ParietariaSPTPPT IgE Specific classesAllergic oral/systemic symptoms
PatientSexAge (years)Clinical symptomsPattern of symptomsDuration of disease (years)Pp.n.Hp.n.Total IgE (U/ml)Pp.n.After eating p.n.
  1. P: Parietaria; R: rhinitis; A: bronchial asthma; C: conjunctivitis; Per.: perennial; S: seasonal; H: histamine (positive control). *All these subjects occasionally ate pistachio.

CMM15R+APer. 8.3 22.512.619.819.8 6020+
CEF 8R+AS 1.6 38.528.728.520.615031+
PFF37R+CS10.3 62.6 9.112.5 7.8 4431+
ULM20R+CS 4.5 50.2 8.219.5 8.336441+
SAM26R+AS 8.4 28.727.629.319.627621+
DPDM28R+C+AS10.1 63.938.519.212.811441
HGF23RS 5.7 18.519.828.812.5 3820
FOF52R+APer. 7.2132.712.863.620.614840
MAM26R+C+AS 6.8 63.819.638.713.517340
FDM14R+CS11.6 50.215.528.2 7.612540
DNAM 9R+AS 1.9 60.612.519.3 7.919831

As far as we are aware, apart from our earlier study (3), there are no reports of a correlation between Parietaria sensitization and pistachio nut sensitization in patients with respiratory allergy. The interesting finding to emerge from our data is that all patients with pistachio nut sensitization suffered from Parietaria-related respiratory symptoms. The other finding is that sensitization to pistachio nut allergens rarely induces severe clinical symptoms. In fact, symptoms were mild in the five patients sensitized to pistachio nut. Unlike our two earlier patients, who frequently ate large amounts of pistachio nuts and had severe symptoms (3), the subjects described herein reported sporadic ingestions of these nuts and had mild symptoms. Thus, it is conceivable that a high intake of this food (be it as roasted nuts or as an ingredient of other foods) is related to a higher risk of developing allergic symptoms.

Because of the low degree of serologic sensitization to pistachio nut in our patients, we did not do SDS–PAGE, immunoblotting, or RAST-inhibition studies.

In conclusion, given the high frequency of Parietaria pollinosis in the Mediterranean area (5, 6) and the increasing consumption of pistachio nut, we suggest that patients affected by this disorder undergo SPT for pistachio.

Acknowledgments

  1. Top of page
  2. Acknowledgments
  3. References

We are greatly indebted to Jean Gilder for substantial editing of the text and to Anna Maria Livolsi, BSc, for technical assistance.

References

  1. Top of page
  2. Acknowledgments
  3. References
Footnotes
  1. Patients with Parietaria pollinosis should undergo allergy testing for pistachio nut if they frequently eat this food.