In the conditioning exercise the human and llama learn what to expect from each other and develop a working relationship. We recommend that a llama be over three years of age before serious pack weights are loaded. Before that keep the training weights much lighter. Some do bite when they get angry, hurt or threatened. Some may just have nasty temperaments.
Llamas are pretty much the same.
Some, out of fear, anger, mistreatment, anxiety, or warped personality, may spit on people, too. In fact, it washes off quite readily. It does smell. My advice is just don't get between two angry llamas. Llamas cost an arm and a leg to buy.