Thank you for your recent inquiry.
Pumpkin allergy has been reported in the literature. The references copied below point out some of these reports, and also discuss pumpkin as an allergen (1-7).
You can investigate pumpkin as a possible cause of your patient's urticarial reaction in two ways:
An ImmunoCap is available for pumpkin seed. Although the degree of cross-reactivity between pumpkin seed and the pumpkin pulp has not been completely worked out, there is evidence to indicate that cross-reactivity does exist. Thus a positive test to pumpkin seed would be strong evidence that pumpkin was the culprit. Unfortunately a negative test would not rule out this possibility.
You could do a prick-to-prick test (prick fresh pumpkin or use the source of pumpkin that the child ate, and then using the same device prick the skin).
If there is a positive ImmunoCap and/or prick test, you should note that there is possible cross-reactivity between pumpkin, muskmelon, watermelon, cucumber, and zucchini (see Reference 4).
Thank you again for your inquiry and we hope this response is helpful to you.
Nielsen KK, Nielsen JE, Madrid SM, Mikkelsen JD. Characterization of a new antifungal chitin-binding peptide from sugar beet leaves. Plant Physiol 1997;113(1):83-91. Berglund L, Brunstedt J, Nielsen KK, Chen Z, Mikkelsen JD, Marcker KA. A proline-rich chitinase from Beta vulgaris. Plant Mol Biol 1995;27(1):211-6. Nielsen KK, Nielsen JE, Madrid SM, Mikkelsen JD. New antifungal proteins from sugar beet (Beta vulgaris L.) showing homology to non-specific lipid transfer proteins. Plant Mol Biol 1996;31(3):539-52.
Yman L. Botanical relations and immuno-logical cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09. La Shell MS, Otto HF, Whisman BA, Waibel KH, White AA, Calabria CW. Allergy to pumpkin and crossreactivity to pollens and other foods. Ann Allergy Asthma Immunol. 2010 Feb;104(2):178-80.
González De Olano D, González-Mancebo E, Macadán SS, Cano MG, Pérez-Gordo M, Ortega BC, Vivanco F, Vargas CP. Allergy to pumpkin with cyclophilin as the relevant allergen. Ann Allergy Asthma Immunol. 2010 Jan;104(1):98-9.
Figueredo E, Cuesta-Herranz J, Minguez A, Vidarte L, Pastor C, De Las Heras M, Vivanco F, Lahoz C. Allergy to pumpkin and cross-reactivity to other Cucurbitaceae fruits. J Allergy Clin Immunol. 2000 Aug;106(2):402-3. Sincerely, Phil Lieberman, M.D.