Heat stress is a significant environmental challenge in poultry production, affecting both broilers and laying hens. The detrimental effects of heat stress include reduced growth, egg production, and quality, as well as decreased welfare and safety. Birds exhibit behavioral and physiological responses to heat stress, such as increased panting, reduced feeding, and altered thermoregulation. These responses can lead to decreased feed intake, impaired immune function, and increased susceptibility to pathogens. Heat stress also affects the intestinal microbiome, increasing permeability and the risk of pathogen translocation. Despite extensive research, the mechanisms underlying these effects remain partially understood, and effective interventions are often inconsistent. Future studies should focus on improving our understanding of the basic mechanisms and developing more consistent and effective interventions to mitigate the negative impacts of heat stress on poultry production.Heat stress is a significant environmental challenge in poultry production, affecting both broilers and laying hens. The detrimental effects of heat stress include reduced growth, egg production, and quality, as well as decreased welfare and safety. Birds exhibit behavioral and physiological responses to heat stress, such as increased panting, reduced feeding, and altered thermoregulation. These responses can lead to decreased feed intake, impaired immune function, and increased susceptibility to pathogens. Heat stress also affects the intestinal microbiome, increasing permeability and the risk of pathogen translocation. Despite extensive research, the mechanisms underlying these effects remain partially understood, and effective interventions are often inconsistent. Future studies should focus on improving our understanding of the basic mechanisms and developing more consistent and effective interventions to mitigate the negative impacts of heat stress on poultry production.