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Mustard allergy is a not-uncommon disorder that can induce severe reactions. Significant associations with mugwort pollinosis and several plant-derived food allergies are demonstrated, suggesting a new mustard-mugwort allergy syndrome. A relationship between this syndrome and food-dependent exercise-induced anaphylaxis is also reported.

Penicillins are immunogenic when administered to humans and in some instances they can also be allergenic, inducing specific IgE antibodies. Whilst the major haptenic group, the penicilloyl, is well characterised, less is known about the relative importance of the different parts of the structure for antibody binding and how this can influence the specificity of patients response. In order to investigate this further, sera from subjects who had suffered an IgE-mediated reaction to penicillins were studied using the radioallergosorbent test (RAST) and RAST inhibition. The assays employed reagents related to the penicillins causing the reaction. Using 173 sera, positive RAST results were only found with reagents based on benzyl penicillin (BP) and amoxicillin (AX). Fifty-three positive sera were selected for further studies and categorized into three groups: (A) sera only RAST positive to AX, (B) sera only positive to BP and (C) sera positive to both penicillins. RAST inhibition studies were then carried out using monomeric penicilloyl conjugates and compounds representing parts of the penicilloyl structures of BP and AX. For all three groups, monomeric penicilloyl conjugates were the most efficient inhibitors but there were differences for the other compounds. Group A sera were also inhibited by the side chain of amoxicillin, whereas group B sera were poorly inhibited by all other inhibitors. Group C sera showed two patterns of inhibition, both consistent with their more cross-reactive profile. Some group C sera were similar to group B, showing inhibition with monomeric penicilloyl conjugates only, whilst others were similar to group A showing inhibition with side-chain-related compounds, although in these cases all the side chain compounds inhibited all the assays. We conclude that in sera from patients allergic to penicillins, IgE antibodies of different specificities can be found reflecting the involvement of the penicillins in inducing the allergic reaction. Detailed inhibition analysis indicates that two main groups of antibodies can be distinguished: one where the side chain contributes a unique specificity to the antigen binding site and in which they are positive to AX, and another where most of the structure is required for optimal inhibition. However, a considerable variation in the pattern of recognition of the antigenic determinant was seen. No coexisting antibodies of different specificities were detected in the same patient.

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