Complex sentence: Some amatoxins may cause irritation and severe pain and even damage to the eyes and skin on contact, however they can't be absorbed through the skin or through inhalation and only eating them causes the toxin's effect.
Split into simpler sentences: Some amatoxins may cause irritation and severe pain and even damage to the eyes and skin on contact. However, they can't be absorbed through the skin or through inhalation; only eating them causes the toxin's effect.