Climbing trumpet can cause skin irritation
Incidentally, it is not the flowers that are poisonous, but all parts of the plant - especially the fruits and seeds. However, there is little agreement on how poisonous the plant actually is. Basically, the climbing trumpet is so toxic that it causes skin irritation on contact and vomiting, diarrhea if swallowed.
Risk of confusion: Trumpet flower and angel's trumpet are not the same
The trumpet flower, also known as the climbing trumpet, is often confused with the highly poisonous angel's trumpet. However, the two plants are not related to each other, because the trumpet flower (Campsis) belongs to the trumpet tree family, while the much more dangerous angel's trumpet (Brugmansia) is a nightshade family.
Whenever possible, use gloves when planting and cutting the climbing trumpet to avoid painful rashes and other skin irritations.