The open-jar symbol on a hair product shows its period after opening, often shortened to PAO. A number with M means months: 12M means twelve months after opening. It is not the purchase date or a batch number. Follow the whole label, including any printed date and storage directions.
How do you read the number beside the open jar?
Read the number and the time unit together. A small open jar marked 6M refers to six months after opening; 12M refers to twelve months. These are examples, not default times for all hair products. Check the actual container and box rather than using the symbol from a different bottle as your guide.
The symbol may be small or printed near other marks. Look at the back, base, and outer box in good light. Do not confuse it with the recycling mark. If the number has rubbed off, a clear photo of the rest of the package can help the maker identify the right guidance.
Is the open-jar symbol the same as an expiry date?
No. The open-jar symbol gives a length of time tied to opening. A printed date gives a calendar point and needs to be read with its wording. A batch code identifies a production lot; it is not automatically a date you can decode. Each mark has a different job, even when they sit close together.
For example, buying a product today does not make an earlier printed date disappear. Opening it also does not reset a calendar limit. When more than one mark appears, read them together. If their meaning is unclear, ask the maker before deciding that one allows you to ignore the other.
- Open-jar mark: a use period after opening.
- Printed date: read the wording next to the date.
- Batch code: details the maker can use to identify the lot.
- Receipt date: a purchase record, not proof of when you first opened it.
Why do some hair products have no open-jar symbol?
Label rules differ by market and product type. The FDA says U.S. cosmetics do not have to carry specific shelf lives or expiration dates, though makers remain responsible for their products. A missing symbol is not proof of unlimited use. It is a reason to check the other directions or ask the company for guidance.
Article 19 of the cosmetics rules published on the UK legislation site explains period-after-opening labeling for certain longer-lasting cosmetics, with an exception where the concept is not relevant. Do not assume that every package sold everywhere must use the same mark. Imported packaging and local labels can look different.
For a wider label checklist, see what to look for on a scalp hydrogel label. This guide focuses on time marks, not ingredient order or product claims.
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When should you record the opening date?
Record the date when you first open the product for use. Write it on a small label without covering the directions, warnings, or batch code. You can also keep a phone note with a package photo. The useful record is the date tied to that exact container, not a general memory of when you went shopping.
A simple note might say “opened October 24” beside the product name and year. Add the printed PAO exactly as shown. Keep a separate record for each container if you use two at once. Moving contents into another pot does not give them a new opening date or a fresh use period.
What if you cannot remember when you opened it?
Do not invent a date from how much product is left. Check old photos, notes, or order records for clues, but remember that buying and opening are different events. If you still cannot place the opening date, contact the maker with the product and batch details. Ask what they recommend for that uncertain history.
A half-full bottle could have been used often for a short time or rarely for a long time. The remaining amount does not settle the question. Do not rely on an online batch-code calculator to supply an opening date; a factory code cannot know when you first used the product.
Does the symbol mean the contents are fine until that month?
No. A printed use period does not override poor storage, contamination, or an unexpected change in the product. The FDA notes that heat, moisture, sunlight, and handling can affect cosmetics. Follow storage directions from the start. If the smell, color, or texture changes, pause use and ask the maker rather than relying only on the calendar.
Keep the lid closed and do not add water to stretch the contents. For handling rather than date-reading advice, see keeping a cosmetic jar clean during use. Neither a tidy container nor a normal smell proves that all is well inside.
What should you ask the maker if the label is unclear?
Ask which date or use period applies to your exact product, whether it starts at opening, and what the storage directions mean. Include photos of the container, the box, and any batch code. Explain if the opening date is unknown or the product was exposed to unusual heat. Those facts are more useful than a guess.
This article does not assign a shelf life to Deoxylocks or any other named product. Check the current package and ask the brand for product-specific details. A general example such as 12M is there to explain a symbol, not to replace the wording on your own jar.
What else do people ask about open-jar symbols?
The most useful distinction is between a duration, a calendar date, and a batch identifier. Keep all three attached to the original product. The answers below address common points of confusion without setting a universal discard schedule. Different formulas and packages can carry different directions, so one bottle should not set the rule for the rest.
Does M mean minutes?
No. Beside the open-jar symbol, M means months. It is not an instruction about how long to leave the product on your hair.
Does 12M start when I buy the bottle?
It refers to the period after opening, not the purchase date. Follow any separate printed date too.
Does closing the lid restart the clock?
No. Closing it is good handling, but it does not make the contents newly opened again.
Can I use the same time limit for every hair product?
No. Read each package. A shampoo, conditioner, and scalp cosmetic may have different guidance.
Is a batch code enough to work out the PAO?
Not by itself. Ask the maker if no clear period is shown. A batch code is not a substitute for the product’s directions.
Sources: FDA guidance on cosmetic shelf life; cosmetics labeling rules, Article 19. Checked October 24, 2026.
Deoxylocks 5% 2DDR Scalp Hydrogel
A physician-formulated cosmetic hydrogel for nightly scalp care. Non-hormonal, clear and odorless, applied once daily to the scalp. Backed by a 90-day risk-free return policy.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
