Asthma is a serious health problem affecting all age groups. Melatonin or its agonists are commonly used to treat many diseases, but there are conflicting data on asthma therapy. This paper analyzes researches on the possible use of melatonin in the therapy of asthma. Melatonin is a potent antioxidant and a vasodilator, but in some experiments, it can act as a pro-oxidant and a vasoconstrictor, which may depend on the duration of use. It has been suggested that circadian rhythms should be corrected in asthmatics to optimize the desired effects of drugs and to reduce the severity of their adverse reactions. Disordered diurnal variations in the salivary levels of melatonin and cortisol are detectable in patients with asthma and may be implicated in its pathogenesis. In addition, the conflicting data on the effect of melatonin on the development of asthma are associated with an incomplete view of the factors influencing the level of melatonin. Thus, to study the effects of melatonin, it is necessary to take into account the greatest possible factors that may influence the level of melatonin and the course of asthma: a daily diet in terms of the use of caffeine, alcohol, sleep-wakefulness pattern, sleep quality proper, and drowsiness during the daytime, social burden, the level of anxiety and stress resistance, and to investigate the levels of endogenous melatonin or its derivatives, immune status, oxidative stress intensity, etc. Obviously, the use of melatonin in the therapy of asthma can be considered, by applying a personalized approach.