Excerpts from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4387229/:
N. sativa and its constituents have been traditionally used to alleviate respiratory disorders such as asthma, bronchospasm and chest congestion (38, 39). Nigellone, a carbonyl polymer of thymoquinone, was shown to be an effective prophylactic agent in asthma and bronchitis with higher efficacy in children than in adults (40, 41). Chakravarty (42) concluded that the nigellone inhibit effectively the histamine release from the mast cells, thus showing the basis for its traditional use in asthma. It was also suggested that N. sativa volatile oil might be a potentially useful respiratory stimulant (43). The antihistaminic effect of the plant was also reported (44, 45).