Proteins that come out of solution and become visible are said to have precipitated.
Precipitation occurs when the protein configurations get altered due to factors such as improper storage conditions (e.g. freezing or prolonged heat exposure). As the protein structures change, they may clump together to form larger particles that are visible to the eye. These precipitates tend to appear as light-colored particles that float around, giving the extract a cloudy appearance.
While it has not been evaluated whether precipitation impacts the overall potency of the product, precipitation is a quality issue that should be brought to the attention of the manufacturer. This is especially true for any recently purchased or unopened vials. Older vials that have been in use for a long time may simply need to be replaced.
If you notice precipitation in your extract, please contact your allergen extract supplier for assistance.