Alarmins, proposed in 2004, as a kind of endogenous mediators are characterized by chemotactic and activating effects on natural immune cells and augmentation of innate and adaptive immune response. At present, defensins, cathelicidins, eosinophil-derived neurotoxin and high mobility group proteins have been recognized as members of alarmins, they are rapidly released from where they are stored in response to infection or tissue injury. As alarmins can promot antigen uptake, processing and presentation, they have the capacity of induction of antigen-specific immune response and can be a kind of ideal adjuvant. In-depth study of the alarmins will help to clarify its position in the immune system, and may provide new means or target of immunotherapy.