Eichner radiation is a type of radiation.
In 2294 and 2295, it was found that this radiation was capable of stimulating growth in mutated strains of plasma plague, developed by Doctor Susan Nuress during an outbreak of plasma plague on Oby VI.
In 2365, this radiation was found to be generated by the alien Ian Andrew, Counselor Troi's son. When he realized his emissions were endangering the crew, he left the ship. After he left, the crew realized he was an unknown lifeform. (TNG: "The Child")