<em>Nigella sativa</em> (Black Cumin) Seed Extract Alleviates Symptoms of Allergic Diarrhea in Mice, Involving Opioid Receptors

<div><p>The incidence of food hypersensitivity and food allergies is on the rise and new treatment approaches are needed. We investigated whether <em>N. sativa</em>, one of its components, thymoquinone, or synthetic opioid receptor (OR)-agonists can alleviate food allergy. Hence, ovalbumin (OVA) -sensitized <em>BALB/c</em>-mice were pre-treated either with a hexanic <em>N. sativa</em> seed extract, thymoquinone, kappa- (U50'4889) or mu-OR-agonists (DAMGO) and subsequently challenged intra-gastrically with OVA. All 4 treatments significantly decreased clinical scores of OVA-induced diarrhea. <em>N. sativa</em> seed extract, thymoquinone, and U50'488 also decreased intestinal mast cell numbers and plasma mouse mast cell protease-1 (MMCP-1). DAMGO, in contrast, had no effect on mast cell parameters but decreased IFNγ, IL-4, IL-5, and IL-10 concentration after <em>ex vivo</em> re-stimulation of mesenteric lymphocytes. The effects on allergy symptoms were reversible by OR-antagonist pre-treatment, whereas most of the effects on immunological parameter were not. We demonstrate that <em>N. sativa</em> seed extract significantly improves symptoms and immune parameters in murine OVA-induced allergic diarrhea; this effect is at least partially mediated by thymoquinone. ORs may also be involved and could be a new target for intestinal allergy symptom alleviation. <em>N. sativa</em> seed extract seems to be a promising candidate for nutritional interventions in humans with food allergy.</p>