Antimatter radiation is an energy form which can be extremely hazardous to humanoid life. A byproduct of antimatter, prolonged exposure to this radiation could cause radiation poisoning and serious degenerative health effects and, in high enough concentrations, could even disintegrate organic tissue. (VOY: "Revulsion", "Friendship One")
In 2375, The Doctor asked Harry Kim if he had come into contact with antimatter radiation as a possible explanation for why Kim's skin was glowing. (VOY: "The Disease")
In 2378, the crew of the USS Voyager, while on their first official mission for Starfleet since being stranded in the Delta Quadrant, encountered a planet whose atmosphere had been contaminated by high levels of antimatter radiation. As a result of their exposure, the planet's inhabitants had developed serious health problems including radiation poisoning, birth defects, and tissue damage. The Voyager crew soon came to learn that Friendship 1, a probe launched by Earth in 2067, was the cause of environmental damage. Encountering the probe, the inhabitants examined its antimatter-based propulsion system, extrapolated it and developed their own energy-generation technology based on antimatter. However, a containment failure released a large amount of antimatter, resulting in the radiation poisoning. Eventually, the Voyager crew were able to reverse the damage by utilizing specially-modified photon torpedoes to deliver a catalytic agent which created an isolytic chain reaction, recombining the nucleonic particles in the planet's atmosphere. (VOY: "Friendship One")