No, saliva itself doesn't inherently "expire" in the same way perishable food does. However, the usefulness of saliva for certain purposes, like DNA testing or medical diagnostics, is time-limited. The stability of saliva components and its suitability for analysis depend heavily on storage conditions and the intended application.
Saliva Stability and Storage
Several sources indicate that saliva can remain stable for a considerable period under specific conditions:
-
Extended Stability: Research shows that certain salivary components, like total organic substances (TOS), total antioxidant capacity (TAC), and oxidative stress index (OSI), are preserved for up to 60 days, regardless of temperature. [Reference: The present results confirm that salivary TOS, TAC and OSI are preserved in samples stored up to 60 days, regardless of temperature.]
-
DNA Testing Kits: Companies like 23andMe provide saliva collection kits with a "Collect saliva by" date. While the saliva itself may not degrade rapidly, the kit's components and the stability of DNA within the sample are crucial. Some sources suggest the sample might be usable for several months after the suggested collection date if proper stabilization buffer is added. [Reference: Quora - For 23andMe, does saliva have an expiration date? and 23andMe DNA Test Kit Replacement Policy]
-
Saliva Test Kits: The expiration date on some saliva-based testing kits, particularly those used for COVID-19 testing, can be extended under specific conditions. For example, the expiration date of Spectrum kits used for Test Iowa saliva samples has been extended to a year from the original expiration date on the kit. [Reference: Saliva kit (spectrum solution) expiration dates extended]
-
Refrigeration: Saliva can be refrigerated for up to a week before needing to be added to a stabilizing fluid in a collection tube. [Reference: Collecting a Saliva Sample]
Factors Affecting Saliva's Usefulness
Several factors influence how long saliva remains suitable for different applications:
- Storage conditions: Temperature and exposure to light greatly impact the stability of saliva components.
- Intended use: Saliva used for DNA analysis has different stability requirements compared to saliva used for a medical test.
- Stabilizing solutions: The addition of stabilizing fluids significantly prolongs the usability of saliva samples.
Conclusion
While saliva itself doesn't spoil, its suitability for various purposes is time-sensitive and depends on how it's handled and stored. The use-by date is often tied to the collection kit or the specific test being conducted, not the saliva itself.
