Chemicals antigenic contaminants

Chemical fixation is not the only factor that causes loss or irreversible masking of antigens. Treatments such as dehydration and embedding following fixation also play a role in the loss of immunorecognition of antigens. Absolute ethanol and xylene must not contain traces of water, and the water bath should be very free from contaminants such as bacteria, fungi, dust, and dirt. Once the sections are contaminated, they cannot be decontaminated. 

Apart from the aforementioned food additives, used intentionally and inevitably in food products, foodstuffs can also contain unwanted components originating from (chemical) pollution or (microbiological) contamination (e.g., antigens of microbial cells and metabolites produced by microorganisms like enzymes, toxins), which likewise are not encompassed by the definition of food additives but can be harmful to human health when found in food products. 

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