Patients with
hypersensitivity to food documented by a double-blind, placebo-controlled oral food challenge have been reported to have a high rate of release of
histamine from basophils in vitro. To determine whether patients with
atopic dermatitis and
food hypersensitivity had similar high rates of spontaneous histamine release in vitro, whether dietary elimination of relevant food
antigens affected this release, and whether a
cytokine,
histamine-releasing factor, could account for it, we evaluated 63 patients with
atopic dermatitis and
food hypersensitivity (38 of whom had eliminated the offending foods from their diets), 20 patients with
atopic dermatitis without
food hypersensitivity, and 18 normal volunteers. Patients with
atopic dermatitis and
food hypersensitivity were found to have higher rates of spontaneous release of
histamine from basophils than controls (mean +/- SE, 35.1 +/- 3.9 percent vs. 2.3 +/- 0.2 percent; P less than 0.001). Those who had eliminated the offending food
allergen from the diet for an extended period had a significantly lower rate of histamine release (3.7 +/- 0.5 percent; P less than 0.001). In patients with
atopic dermatitis without
food hypersensitivity, the rate (1.8 +/- 0.2 percent) did not differ from that in normal controls. Mononuclear cells from persons with
food allergies spontaneously produced a
histamine-releasing factor in vitro that provoked the release of
histamine from the basophils of other food-sensitive persons, but not from those of normal controls. Patients who adhered to a restricted diet had a decline in the rate of spontaneous generation of the factor by their mononuclear cells. The
histamine-releasing factor was found to activate basophils through surface-bound
IgE. We conclude that in patients with
food hypersensitivity, exposure to the relevant
antigens produces a
cytokine (
histamine-releasing factor) that interacts with
IgE bound to the surface of basophils, causing them to release
histamine.