Induction of immunological tolerance by oral administration of nickel and chromium

Oral administration of nickel-chromium to guinea pigs by way of a fixed occlusal splint, or the incorporation of metallic powder or salts into the pelleted food, did not induce hypersensitivity to these metals. In addition, a subsequent attempt to immunize the pre-treated guinea pigs failed in most animals, whereas non-pre-treated guinea pigs became clearly hypersensitive. These results show that oral administration of nickel and chromium induced a state of (partial) tolerance to both metals.