All over-the-counter skin care products containing salicylic acid are required to have an expiration date on the packaging. But is it safe and effective to use salicylic acid after the expiration date?
Salicylic acid is a stable compound that degrades very slowly if stored in optimal conditions. So yes, as a general rule, salicylic acid products can be used long after their expiration date as long as they have been stored properly.
Each individual product is different however. They all have different ingredients and packaging quality. Check yours for any of the following signs of degradation and spoiling: the product has changed color or texture, or the smell is off putting or rancid.
Also check for dark speckles of color, as this is an indication of bacterial contamination. If any of these signs are present in your product, discard it and do not use regardless of the expiration date.
Storage conditions that promote a longer shelf life for salicylic acid
Proper and optimal storage is key to the shelf life of salicylic acid. Exposure to light degrades and destroys the medicinal properties of salicylic acid over time. Thus, most salicylic acid products are smartly packaged in opaque containers which effectively prevent light from reaching and degrading the product.
Storing salicylic acid inside a cabinet or cupboard helps protect it from light. If exposed to direct sunlight/UV light, salicylic acid will degrade quickly. Incandescent, fluorescent, and even LED light will degrade salicylic acid also, but more slowly.
Salicylic acid should also be stored in a tightly sealed, airtight container in order to prevent deterioration. Exposure to oxygen promotes the degradation of salicylic acid. Salicylic acid has natural antibacterial properties, so bacterial contamination is less of a concern.
When not stored in an airtight container, the water base of a liquid solution will evaporate. This causes the concentration of salicylic acid to increase. In over-the-counter salicylic acid skincare products, the percentage of salicylic acid ranges anywhere from less than 1% to up to 30%, depending on its intended use and purpose. Wart removal products usually contain between 17% and 30% salicylic acid.
Evaporation of the liquid base causes the salicylic acid concentration to be higher than indicated on the label. The product will be stronger and harsher than intended. This has the potential to cause skin burning and other unintended results. So, one last recommendation:
Safety guideline when using expired salicylic acid
When using old salicylic acid after its expiration date, you should always test a tiny portion of the product on a small area of skin. If possible, choose an area of the body that is easily hidden and not noticeable for testing. Wait a few hours and check that the product is working as it should. If so, then you may safely apply the salicylic acid to other locations.
In conclusion, usually expired salicylic acid products will work just fine. But sometimes you will find that old salicylic acid is spoiled, or more or less effective than it should be. Just test it first to be safe, and if necessary toss the container and replace it with the new one.