Tolerance to infections, or disease tolerance, is one of the mechanisms host organisms can fight against parasites, pathogens or herbivores that attack the host. Tolerance to infections is defined as the ability of a host to limit the impact of parasites, pathogens or herbivores on host health, performance, and ultimately on fitness. Tolerance is not equivalent to resistance. Disease resistance is the host trait that prevents infection or reduces the number of pathogens, parasites and herbivores within or on a host.