There is only one possible danger involved in raising a Chansey or Blissey. Studies have shown that long term consumption of their eggs can lead to an addiction. Individuals with an addiction find themselves unable to feel happy without an egg, and often become chronically depressed. These individuals have been known to purposely injure themselves just to get into a hospital where they can get an egg.
Hazards
...So would you say those people are addicted to eggstacy?
Q: What Pokémon is good at treating colds? A: Cyn-Day-Quil®