D3.222 - Contact urticaria to raw potato possible due to cross-reactivity with birch pollen

Potato also known as Solanum tuberosum L. from Solanaceae family is cultivated in all regions around the world and is widely used for consumption. Immediate reactions against raw potato have been reported in adults, with mostly being in the form of contact urticaria or dermatitis, rhino-conjunctivitis, asthma and rarely anaphylaxis. Raw potato hypersensitivity reaction is believed to occur due to IgE cross-reactivity with birch, grass or mugwort pollen, tomato and latex. 

We report a 52-year-old woman, with early spring allergic rhinoconjunctivitis, positive skin prick test to Betulaceae sp. pollen extracts and a history of oral allergy syndrome to raw vegetables and fruits (apple, pear, hazelnut, carrot, kiwi, peach, apricot, plum and cherry) and contact urticaria associated with conjunctivitis after peeling raw potato to which prick-prick skin tests were also positive. There are no reactions after ingestion or contact with cooked potatoes and no contact reaction with latex products. Molecular diagnosis was also performed with an in vitro allergy explorer using IgE multiplex immunoassay test, integrating cross-reactive carbohydrate determinants inhibitor.

Allergy skin prick tests were positive for commercial pollen extracts from Betulaceae sp (8 mm wheal) and hazelnut (6 mm wheal). Prick-prick tests were positive for apple (20 mm wheal), pear (5 mm wheal), carrot (8 mm wheal) kiwi (6 mm wheal), peach (7 mm wheal), apricot (5 mm wheal), cherry (5 mm wheal), plum (4 mm wheal) and raw potato (10 mm wheal). Specific serum IgE revealed IgE mediated sensitization to birch pollen Bet v 1 (9.86 kUA/L), Cor a 1.01 (9.61 kUA/L) and Fag s 1 (9.70 kUA/L). Other IgE sensitizations in vitro were detected to PR-10 like Cor a 1.04, Mal d 1, Fra a 1 and Gly m 4, but not to potato extract or latex allergen components. 

Our results indicate that sensitization to potato is not a marker of isolated allergy to potato, but rather due to cross-reactivity with birch pollen. Using a multiplex allergy explorer test is useful in clinical practice to assess the detailed IgE sensitization profile in individual cases, when pollen-food allergy syndromes are suspected.