Odour and odorants may affect the quality of life of exposed individuals. A review of the literature on olfaction and reactions to odours was carried out with the aim of reaching an understanding of their influence on well-being and health, and to suggest possible improvements in odour environment. This review has focussed specifically on the impact of animal production emissions. Factors like emission and air movements form the physical odour levels, and individual parameters involving psychological and social factors determine the human response. An odour may have positive as well as negative effects on well-being. Learning may be important for induced approach or avoidance behaviour. Common sites of irritation and injury from odorants are the respiratory organs and the nose. In most cases, the protection system triggered by the trigeminal nerve prevents severe effects. Increased frequencies of a number of respiratory and stress-related symptoms are found in the vicinity of animal production facilities. Explanations may be odour-mediated symptoms through annoyance and/or co-existing compounds like dust and gases with synergistic effects. Besides hydrogen sulphide, a number of gases related to animal production have hazardous properties and might be contributory elements despite their low concentrations. Important factors affecting mood, stress, and perceived health are odour levels, exposure time, sensitivity, unpleasantness, cognition and coping. Odour unpleasantness influences annoyance and might be interesting for regulatory purposes.