Chemical ecology studies the structure, origin and function of the chemicals involved in the interactions of living organisms and their impact on ecology, evolution and behavior of organisms interact.

These chemicals are known as semiochemicals, are natural products, ie products of secondary metabolism, produced for a specific purpose by living plant or animal organisms, without participating in the basic organic function. Natural products cover needs vital to their organizations, such as the chemical communication and chemical protection. Organisations in perpetual search for food, mates and maintenance, repel enemies and try to survive by using chemicals that they produce.
Chemical ecology is essentially an interdisciplinary field that combines the fields of Chemistry and Biology. On the chemical side, it includes the study of natural products chemistry (isolation, identification), biochemistry (metabolic pathways), mechanistic studies, and synthetic organic chemistry. On the biological field, it deals with the investigation of the ecological roles of chemicals (behavioral studies, electrophysiological reactions).
Depending on the function of a semiochemical, this group of chemicals can be further divided into three classes: pheromones, allomones and kairomones. Pheromones are chemical substances used to carry chemical messages between individuals of the same species. They are divided into pheromones of direct response and physiological action. The first category includes sex pheromones, aggregation, markers, alarm or defense, territorial ownership, while the latter is characterized by pheromones cause functional and hormonal changes.
Kairomones and allomones are characterized as allelochemical substances, and are used to transfer messages between individuals of different species. The former have a positive effect to the receiver and include attractive food substances that help herbivore insects to find food, predators to locate their victims and parasites their hosts.  The latter have a beneficial effect to producer and their role is mainly defensive.
Initially, chemical ecology was focused mainly on the study of pheromones in social insects (ants, bees, wasps, and termites) as a means of communication for social organization. Plants, also, use numerous chemicals for protection against competitors, pathogens, herbivores, and abiotic factors such as temperature and radiation. In recent years, studies of natural products of other organisms such as mammals, marine animals or even microorganisms are under investigation.
The field of chemical ecology has evolved into a science with a variety of practical applications in the areas of pharmaceutical science, and alternative forms of plant protection, environmentally friendly. The substances used by organizations to repel enemies and to protect themselves have become objects of research efforts for the discovery of new drugs, substances to improve the human health and nutrition and modern means of combating diseases of plants and animals.