Allergic reactions to the Australian paralysis tick, Ixodes holocyclus: diagnostic evaluation by skin test and radioimmunoassay.

Allergic reactions to Ixodes holocyclus are well recognized but poorly defined. Tick-bite reactions in 42 individuals in this study fell into six classes. Skin-prick tests and radioimmunoassay (RIA) indicated that all systemic hypersensitivity (class 3) and atypical reactions (class 4) were IgE-mediated. Some 73% of the large local reactions (class 2) and only 12.5% of the small local reactions (class 1) were associated with IgE specific for tick allergens. Subjects who reported heavy exposure to tick-bite were more likely to have positive RIA values (P less than 0.05). There was an association between the individual's atopic status and tick allergy (P greater than 0.05).