[Ant venoms: a rare cause of allergic reactions in Switzerland]

In Switzerland, unlike other countries, allergic reactions to ants are a rare phenomenon when compared to the well known allergies to bee and wasp venom. In this report we present a series of case reports and a review of the different types of allergy to ants. Due to increased travel and heterogeneity of the population, we have observed several patients with sensitisation or allergy to the venom of imported fire ants (Solenopsis), a species of ant found in the Americas. Furthermore, allergic reactions to bites of the mound-building wood ant (Formica rufa), whose habitat is Central and Northern Europe, have been documented. Whereas reactions to fire ants can be life-threatening, reactions to mound-building wood ants have led to marked local reactions and in 2 cases to dyspnoea and wheezing. These reactions could be due either to primary sensitisation to ant venom or cross-reactivity in the presence of an allergy to wasp venom. Evaluation of patients presenting with a potential ant venom allergy includes a detailed personal history, skin testing and determination of specific IgE. However, to date only extracts from fire ants are commercially available for diagnostic tests. In the light of our observations we assume cross-reactivity between the venoms of fire ants and mound-building wood ants, and it therefore seems appropriate to use fire ant diagnostics in determining sensitisation to mound-building wood ants. In patients with severe fire ant-venom allergy we recommend desensitisation by immunotherapy, whereas in patients presenting with minor allergic reactions, e.g. after bites by mound-building wood ants, we provide the patients with emergency medication. Since current knowledge of ant allergies in Europe is limited, further studies are warranted.