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Appendix A. Skin biopsy of the left calf taken during flare-up shows a slight epidermic atrophy with a lymphocytary infiltrate. Moreover, a mixed infiltrate with perivascular lymphocytes and abundant dermic eosinophils can be observed. In the center of the biopsy a subcorneal pustule constituted by polymorphonuclears, eosinophils and neutrophils can be seen (Hematoxilin-Eosin stain; original magnification x10, x40 respectively).

Sunflower seed is one of the most common edible seeds and its consumption is growing worldwide. Case reports of sunflower seed allergy have been described in the medical literature since the 1970s. However, there are few data on the overall prevalence and clinical manifestations of sunflower seed allergy. We evaluated the clinical and immunological features of 47 patients with sunflower seed allergy diagnosed in the Allergy Department of a tertiary hospital in Madrid over a 5-years period. All of them reported adverse reactions after ingestion of sunflower and had specific sensitization to sunflower seed determined by skin prick test (median 7mm) or specific IgE (median 1.07KU/L). Most had an adult-onset reaction to sunflower seed preceded by a history of atopy and other food allergies diagnosis, predominantly to peach, peanut and nuts. Clinical presentation of sunflower seed allergy in our sample ranged from mild to severe, with a high proportion of patients suffering severe reactions, often undertreated. A variability in the severity of symptoms was seen on repeated exposures to sunflower seed on a same patient. Levels of sunflower seed IgE were strongly correlated with levels of IgE to non specific lipid transfer proteins, while no significant differences were found in the severity of the reactions according sensitization to those proteins. With sunflower seed as a potential severe allergen, further study on the allergenic content and clinical cross reactivity of sunflower seed allergy is required in order to prevent life threatening reactions.

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