Absence of skin sensitivity to oxides of aluminium, silicon, titanium or zirconium in patients with Crohn's disease

Background-Some metallic compounds, especially of zirconium, can cause cell mediated granulomatous inflammation of the skin. Pigment granules containing compounds of aluminium, silicon, and titanium have been observed within macrophages in the wall of the small intestine in health and in Crohn's disease. Zirconium compounds can be ingested in toothpaste. Aim-To determine in a pilot study if granulomatous sensitivity can be detected to compounds of these metals or silicon after injection into the skin of patients with Crohn's disease. Subjects-Eight patients with Crohn's disease known to have had granulomata in the intestine and not currently treated with corticosteroids, and two healthy controls. Method-Two intradermal injections each of 0.1 ml of a 0.02% suspension of one of the compounds made in the abdominal wall of each subject. The site was marked and full thickness skin biopsy performed six weeks later. Result-A foreign body granuloma was observed on histological examination of two biopsy specimens but no evidence of a cell mediated response in any subject. Conclusion-No support was found for the hypothesis that Crohn's disease is due to a specific sensitivity to ingested metallic or silicon compounds.