Look out for the following negative status effects.
Lingering in areas filled with smog will gradually fill the toxicity gauge, so hurry to an area in clean air as soon as possible. Consuming tainted food or water will quickly fill the toxicity gauge. When poisoned, your animal's life will steadily deplete. Toxicity is fatal if untreated, so use healing items to reduce the toxicity gauge.
When making contact with unclean animals, there is a chance you will get fleas. If affected, your animal will occasionally stop to scratch itself, rendering it immobile for a short period. To get rid of fleas, go into water or use flea shampoo. When a Desperate mate is chosen, it will always give the player fleas.