Does lube expire?

Yes. Most lube is good for 1 to 3 years unopened and about a year once opened. The date is printed on the bottle or tube. Separated, discolored or off smelling lube goes in the trash. Expired lube is rarely dangerous, but its preservatives fade and its pH drifts, so irritation and infection risk go up.

Where the date is.

Personal lubricants are regulated as medical devices in the United States, and the expiration date comes from the manufacturer's stability testing rather than a guess. Look for "EXP" or an hourglass symbol on the bottom of the bottle, the crimp of a tube, or the box. Some brands print a batch code and a date. Some print only the batch code, in which case the brand's site or customer service can decode it.

Typical shelf life is 1 to 3 years from manufacture. Once a bottle is open, air and fingers get in, and the common rule of thumb is to finish it within a year.

Signs it has turned.

Water based lube is mostly water, a thickener, a humectant and a preservative system, and it is the first to go. Watch for:

• A watery layer on top or clumps at the bottom (separation)
• A color shift, usually toward yellow
• A sour, chemical or plastic smell where there was none
• A change in texture: thinner, gummier or grainy
• A cap or pump with buildup around the threads

Any one of these is enough. You are not going to save the few dollars left in the bottle.

Why expired lube is a problem.

Two things happen over time. The preservatives lose strength, and preservatives are the only thing stopping bacteria and mold from growing in a bottle of water based gel that gets handled in the dark. The second is that the pH drifts. A good water based lube is adjusted to sit near the vaginal range of 3.8 to 4.5. As it ages, the buffer wears out and the number moves.

Neither change is dramatic. It is the difference between a product that protects the vaginal environment and one that quietly works against it. People who have been using the same bottle for three years and now get irritation they did not used to get are a familiar story.

Silicone lasts longer.

Silicone lube contains no water. With no water there is nothing for bacteria to grow in, nothing to separate and no pH to drift. Uberlube is three ingredients, none of them water. It still carries a date, and it can eventually go cloudy or gummy on the threads of the bottle, which is the sign to replace it. In practice a bottle of silicone lube outlasts several bottles of water based.

Oil based lubes sit in between. Oils go rancid, and the smell tells you when.

What to do with the old bottle.

Throw it out with the trash. Buy a size you will actually finish in a year rather than the value bottle. Store it capped, at room temperature, out of the shower and away from a sunny window.

If an old bottle has already caused burning, itching or a change in discharge that lasts more than a few days, see a clinician. Nothing here is medical advice.