Stability observations are observations of your product’s performance over time (e.g. appearance, colour, odour, pH).
The observations should be recorded and saved in a report, which is stored in your PIF and a consideration of the stability of the product is required in the CSPR.
Do you have any older batches that have been stored / kept? For non-water containing products, for the purposes for the safety assessment, I can accept 1 month at room temperature, generally. But you should continue the observations yourself and record them in the PIF to support the shelf life of the product.
When you do stability testing, try to do it in the final packaging so that you also get information on the packaging compatibility of the product and the pack you have chosen.
Keep some samples from each batch you make, to monitor how they perform at room temperature. After a certain time period, make a note of the appearance, odour and colour and changes (if any), and this will provide evidence to support the shelf-life.
If your product contains water e.g. an oil in water emulsion, one way to check that the emulsion is stable is to store it at elevated temperatures (greater than 35°C) for 3 months which will give an indication of what might happen in the future, when your product might be stored for long-term at room temperature. The ability to store samples at higher temperatures is very difficult to achieve at home and therefore a specialist laboratory can be useful. If you get satisfactory stability results after 3 months you can confidently put a shelf-life of at least 12 months (and many companies use 24 months) on your product.
The following UK-based companies carry out stability tests:
If your product does not contain water: only minimal stability testing is required, such as 1 month at home, in various locations. This will give you evidence to start with a shelf life of 6 months, and as you gain more data you can extend it further.
Special case – soap, dry products: Do not need any stability test in particular.