photoallergy

Etymology tree
Proto-Indo-European *bʰeh₂-
Proto-Indo-European *bʰéh₂os
Proto-Hellenic *pʰáwos
Ancient Greek φᾰ́ος (phắos)
Ancient Greek φῶς (phôs)
Ancient Greek φωτο- (phōto-)der.
English photo-
Proto-Indo-European *h₂el-
Proto-Indo-European *h₂élyos
Proto-Hellenic *áľľos
Ancient Greek ᾰ̓́λλος (ắllos)
Proto-Indo-European *werǵ-
Proto-Indo-European *-om
Proto-Indo-European *wérǵom
Proto-Hellenic *wérgon
Ancient Greek ἔργον (érgon)
German Allergiebor.
English allergy
English photoallergy
From photo- + allergy.