Glossary beginning with P
A common preservative in allergenic extracts. It is bacteriostatic, which means it inhibits the growth of bacteria. The FDA mandates that all multiple dose vials must contain a preservative of some kind to ensure sterility.
Protein Nitrogen Unit. A rough estimate of protein concentration used in non-standardized products. It is based on the nitrogen content, which is an integral part of all protein. One mg (milligram) of nitrogen is equal to 100,000 PNU.