Background: Tomato contains many allergens but their clinical relevance is poorly defined and the usefulness of available diagnostic methods is unknown.

Objective: To assess the clinical usefulness of current diagnostic methods for tomato allergy.

Methods: Ninety-six adults with plant food allergy were grouped based on their reactivity to PR-10, profilin, and lipid transfer protein (LTP). Tomato allergy was ascertained by history and a positive skin prick test (SPT) to fresh tomato. SPT with a commercial extract and immunoglobulin (Ig) E measurements were carried out.

Results: In total, 36%, 8%, 28%, 18%, 8%, and 1% of patients were sensitized to PR-10, profilin, both PR-10 and profilin, LTP alone, LTP plus PR-10 or profilin, and genuine tomato allergens, respectively. Tomato allergy was detected in 32 (33%) of the 96 patients and was significantly associated with profilin hypersensitivity (P<.001). The sensitivity of SPT was good in all subgroups, but specificity was poor in many cases. ImmunoCAP sensitivity was acceptable in profilin reactors, but very poor in PR-10 reactors. IgE levels were not associated with tomato allergy in any of the subgroups. Similarly, birch and peach-specific IgE levels were not associated with tomato allergy in PR- 10/profilin or in LTP reactors, respectively. Both SPT and ImmunoCAP worked well in the only patients with true tomato allergy. Birch- and tomato-specific IgE levels were not associated in patients monosensitized to PR-10, but they were correlated in profilin groups (P<.005). Peach- and tomato-specific IgE levels were correlated (P<.001) in LTP-allergic patients.

Conclusions: Tomato allergy occurs via sensitization towards different proteins. Component-resolved diagnosis helps to define clinical subgroups with different risk levels.

Key words: Tomato. Component-resolved diagnosis. Cross-reactivity. Oral allergy syndrome.