I have a 1 oz dropper of lacsal serum that I bought last february or so. Recently I opened it and noticed it smells different from how it used to? It smells a little like rotten eggs, sulphur-y and kind of sour. I thought maybe it developed a bacterial colony or something. Should I throw it away or would it still work as usual?

Dear missk:

Typically when kept at standard room temperature, LacSal Serum can keep well for years and years.

But if you feel the difference in scent has changed dramatically, feel free to pick up a new batch.

It could be the lactic acid that you are smelling.

Best Wishes,
-Skin Biology