Cosmetic shelf life: the PAO symbol, expiry dates, and when to bin mascara

Cosmetics have two clocks: shelf life before opening (the expiry date, counted from manufacture) and shelf life after opening (the PAO, an open-jar picture with a number and M). Once the lid comes off, air, fingers and brushes carry microbes in every time you use it, so the second clock starts. This lesson covers reading both, telling whether something has gone off, and why mascara needs replacing soonest.

What the symbols on the box mean

On the label	Meaning	Counted from
Open jar + 6M	Use within 6 months of opening	The day you first open it
Open jar + 12M	Use within 12 months of opening	The day you first open it
Hourglass, or “best before end of” + month/year	Use before the end of that month, if stored properly	Manufacture (already printed)
MFG	Manufacture date	—
EXP	Expiry date	—

M stands for month. The PAO (period after opening) symbol comes from EU cosmetics law, and the number is usually in months, sometimes years.

The EU rule: products that stay stable for 30 months or less must print a date of minimum durability. Products that last more than 30 months do not need a date, but must show a PAO instead. Products with no risk of deteriorating after opening, such as sealed pressurised sprays that air cannot get into, or single-use items, may have no PAO.

On Thai-language labels, the Thai FDA requires the month and year of manufacture or of expiry. So many imported products carry a date on the Thai label and a PAO on the original box.

Shelf life before opening

If there is an expiry date, go by it. If there is only a manufacture date and a PAO, under the EU rule that means the maker expects it to stay stable for more than 30 months, unopened and stored properly. “Stored properly” is the condition that matters: a product left in the sun or in a car for months can go off before the date on the label.

In the US, no law requires cosmetics to carry an expiry date. The US FDA treats working out shelf life as the manufacturer’s responsibility.

Example: working out the real bin date

A serum. The Thai label says expiry 08/2027, the box shows PAO 12M, and you open it on 1 November 2026.

1. Count the PAO: 1 Nov 2026 + 12 months = 1 Nov 2027.
2. Compare the expiry date: end of August 2027.
3. Go by whichever comes first: end of August 2027. You get about 10 months of use, not 12.

A jar of cream. PAO 6M, opened 15 January 2027, no expiry date on the label.

1. 15 Jan 2027 + 6 months = 15 July 2027.
2. If you use about 0.5 g twice a day, that is 1 g a day, so a 50 g jar lasts about 50 days. Plenty of margin.
3. But if you use 0.5 g only twice a week, that is 1 g a week. In 26 weeks you use only about 26 g, and more than half the jar is left on the bin date.

The lesson from the second case: for things you use only now and then, a smaller size makes more sense, because the PAO counts time, not how much is left.

Write the opening date on the bottle with a marker on day one. It works far better than trying to remember.

Mascara and eye products

Eye-area products tend to have shorter shelf lives than others. The US FDA says manufacturers usually recommend discarding mascara two to four months after purchase. The reason: the wand touches your lashes and goes back into the tube every time, carrying microbes in.

Rules worth remembering:

• If mascara dries out, throw it away. Never add water or saliva to loosen it: that brings in microbes and dilutes the preservative.
• Do not share, including store testers, which are even more likely to be contaminated.
• With an eye infection or inflamed skin around the eye, stop using all eye-area cosmetics and talk to a doctor.
• Anything you put near your eye must be clean.
• Never apply or remove eye makeup in a moving vehicle.

Example: you open a mascara on 1 November. Two to four months takes you to somewhere between 1 January and 1 March. If you want one easy number, use the earlier one. If it dries out or smells different before then, bin it then.

Signs a product has gone off, whatever the label says

Temperature changes, sunlight and air can change colour and texture, and can make products smell. Look out for:

What you notice	Often seen in
A changed, rancid or sour smell	creams, lotions, lipsticks, anything oil-based
A colour change, darker or yellower	creams, serums, foundation
Water and cream separating and not mixing back when shaken	lotions, creams, liquid foundation
Clumping, drying, hardening	mascara, gel eyeliner
Stinging or itching from something you used to tolerate	anything

The last one matters. If a product gives you a rash, redness or itching, stop using it, and if it does not improve, talk to a doctor or pharmacist. How to test a new product is in the previous lesson, patch testing new products.

Storing products so they make it to the date

Heat breaks down preservatives and makes bacteria and fungi grow faster. The US FDA advises not storing cosmetics above 85°F, about 29°C. In Thailand daytime temperatures are often above that, so take extra care.

• Do not leave them in the car or on a sunny windowsill.
• Close the lid tightly every time.
• Use a spatula for jar creams instead of your fingers.
• Wash your hands before use, and do not share.

Gel polish and nail tools have their own storage needs: see storing gel and nail tools.

Common mistakes

• Counting the PAO from the purchase or manufacture date. It counts from the day you first open it.
• Treating the expiry date as the only deadline. A badly stored product can go off before it.
• Adding water to dried-out mascara. Bin it and open a new one.
• Keeping your makeup bag in a parked car. Heat breaks down the preservatives.
• Not writing down when you opened it, and then having to guess.

Sources

• Shelf Life and Expiration Dating of Cosmetics — U.S. FDA
• Eye Cosmetic Safety — U.S. FDA
• Cosmetic products labelling — Health Products Regulatory Authority (Ireland)
• Regulation (EC) No 1223/2009, Chapter VI Article 19 — legislation.gov.uk
• Check the Thai FDA before buying, patch test before using cosmetics — Thai FDA (in Thai)