Nose - Foreign Material

Foreign material (Figure 1, Figure 2, Figure 3, Figure 4, and Figure 5) refers to inhaled particulate test material or presumed test material. Therefore, this term applies only to inhalation studies or gavage studies in which the test material has been inhaled or exhaled into the nasal cavity. The term "pigmentation" is reserved for endogenous pigments (hemosiderin, lipofuscin) found in the nose and should not be used for exogenous material (see Nose - Pigment ). If the material has the expected morphologic appearance, is found only in treated animals, and increases in amount with increasing exposure level, it may be assumed to be the test agent. The morphologic appearance of the foreign material can be compared to the material found in the lung (Figure 5), where, in inhalation studies, it will usually be more abundant. The term “foreign body” is reserved for inhaled bits of plant material (feed or bedding), hair fragments, or other substances that are found in control and treated animals or do not increase in severity with increasing exposure level (see Nose - Foreign Body ).

It is uncommon to see the test agent in the nose. There may be little response to small amounts of inert particles, but more reactive materials may elicit an inflammatory response and changes in the nasal epithelium (e.g., degeneration or necrosis, metaplasia, atrophy).