Once, I had the bright idea to leave my sunscreen in my car, so I could reapply when needed.  One warm day, I pumped out a little of the lotion with SPF, and it was lumpy and curdled.  I didn’t even know a lotion could do that.  It was a new, 6 ounce tube, and I felt very wasteful.  Store your products in a cool, dry place.

If something smells or separates, toss it. Bacteria loves warmth, humidity, and liquid, so your products are a very good breeding ground for things to go very wrong.