A form of radiation that speeds the growth of some viral strains, and which nearly causes a plasma plague sample to break containment aboard the Enterprise-D.
Eichner radiation is the hidden danger in the Next Generation episode The Child. While the ship is carrying plasma plague specimens to the Rachelis system, one strain begins to multiply and threatens to burst its containment module.
Hester Dealt explains that only Eichner radiation could have that effect, and that the levels found aboard a starship should be far too low. A search fails to find any equipment producing it.
The emissions come from Ian Andrew Troi, the rapidly growing boy born to Deanna Troi. He is an energy being who took human form out of curiosity, and his true nature gives off the radiation. On learning this he gives up his body and leaves, and the growth stops at once.