Allergens and cross-reactivity
The only arachnid allergen characterized so far is Arg r 1, the major allergen from the pigeon tick Argas reflexus (Table 6).153,158,159 Arg r 1 is a lipocalin showing about 20% SI with lipocalins from furry animals and cockroach, and 25–35% identity with other tick lipocalins.158Cross-reactivity has been suggested between bee and tick allergens152 and between scorpions and fire ants155 based on whole venoms or WBE but has not yet been investigated on a molecular level. Scorpion venoms contain class III PLA2s with high structural similarity to honey bee venom Api m 1 and an overall SI of 35-40%.