Almost all shoppers are used to checking expiration dates on food, but when it comes to skincare, only a fraction of people have noticed that often tiny jar marked with “6M” or “12M” or “24M” on their favourite serum or moisturiser.

Those figures refer to how long after opening a bottle the manufacturer believes the product should be good for, but as Dr. Emma Meredith, director-general of the Cosmetic, Toiletry and Perfumery Association, the UK’s personal care trade body, “this is not an expiration date.”

“It’s an indication to the user that, once opened, the product will not deteriorate to cause harm to human health within that time period,” she said.

Basically, Meredith explains that a consumer isn’t going to get microbial contamination at an unacceptable level within the prescribed time frame. However, what you’re far less likely to see is a date stamped on a product telling you that, even unopened, it has to be used before then. In fact, in the US, the only products that have to be marked in this way are drug products, such as sunscreen, while in the UK and EU, you’ll only see a “best before end” date on products that have a shelf life of under 30 months.

While, legally, all products must be stability-tested to ensure that, unopened, after several years they will still look, smell and feel the same as when they were first produced, there is no similar obligation to test for efficacy — something that might surprise consumers, and has, in recent years, been one of those conversations that cosmetic chemists and formulators have in hushed tones at conferences.

“The reason why people are starting to talk about this is because the industry today is much more focused on performance-driven skincare,” said Dr. Mike Bell, head of science research at the No7 Beauty Company, which is part of the Walgreens Boots Alliance. “Consumer expectation is higher, so that has driven focus on high-performing actives, such as vitamin C and retinol.”

The problem is that while these actives can be highly effective when it comes to tackling, say, pigmentation and fine lines, their efficacy can diminish very quickly, even when the packaging hasn’t been opened. Product claims are based on tests or clinical trials that are carried out using an item that has come straight off the production line, but the consumer, who might buy the product based on the results it promises, has no way of knowing whether their tube or bottle was produced two weeks ago, or two years ago.

A Storm Is Brewing

This issue isn’t yet something that’s widely discussed among beauty consumers, but as increasingly science-conscious shoppers get more savvy, it’s undoubtedly a question that brands are going to have to face head on.

So what is the answer? Dermatica, a service that offers remote consultations for prescription skincare, and now also sells its own range of non-prescription skincare, believes it’s about manufacturing small batches of products that are shipped direct to the consumer. Last year, it began selling their Vitamin C 15%: Fresh Batch Ascorbic Acid in the UK; the timeline for a US launch of the product has not yet been finalised.

“L-Ascorbic acid is the most potent form of vitamin C,” said Mohini Patel, lead physical product manager at Dermatica. “However, it’s very unstable and when it starts to degrade, efficacy drops. Derivatives may be more stable but they need to go through conversion pathways on the skin which means by the time you’ve actually got ascorbic acid, it’s at a lower concentration.”

The brand’s solution is to produce small batches that are packed in airtight, opaque bottles, shipped fresh and designed to be used within a month — although they say they have data to show that even after 90 days, ascorbic acid levels remain at 15 percent.

That short time period might be possible as a DTC brand, but for those reliant on retailers, a quick turnaround time is arguably unattainable.

“Once you’ve sent a product to a retailer, you don’t know how it’s stored — or for how long,” said Dimitra Davidson, president and founder of Indeed Labs. Despite this, she believes that brands need to take this into account. “The onus is on the brand to run stability tests on products as they get closer and closer to the end of their shelf life to check that they’re still good.”

Unintended Consequences

But while small batch processing and short expiration dates are one approach, Davidson believes that this could lead to unintended — and undesirable — consequences, such as increased prices and more waste.

“Unlike food or drugs, which might pose health risks if used after expiration, skincare products generally don’t carry the same threat,” she said, adding that you also run the risk of “creating extra fear and misunderstanding with the consumer.”

Davidson also said it’s important to put these things in perspective. She believes that looking at the potential diminished efficacy of an active ingredient after a certain period of time “in isolation of everything else in the consumer journey” means that we risk over-amplifying its importance.

This might be a sigh of relief for brands and consumers alike as small batch, or on-demand, production is hugely expensive. Inevitably, those increased production costs would be passed on to consumers. There’s also the problem of what to do with expired products. At a time when the beauty industry is being scrutinised for its sustainability credentials, the idea that you might have to send products that are not harmful, but simply less effective, to landfills, doesn’t sit right with many in the industry.

The Science Solution

Combining smart sales forecasting with clever formulation and packaging looks to be as close as the industry might be able to get to a definitive solution.

For Dr. Bell, it’s about formulators understanding the “dose response” — or what levels of an ingredient are required to effect the change that you want, whether it’s a reduction in fine lines or improving pigmentation. Then it’s about knowing how a reduction in efficacy will impact these levels and whether you’ve still got enough of the active to have an impact. That, and compromise.

“It’s a balance between using a derivative that might not initially be as effective as a more potent but less stable form of the active, but after several years, is still going to deliver about the same levels of efficacy that it was delivering at the start.”

He also points out that while there is no legal obligation to test products for efficacy after subjecting them to stability testing, it is straightforward to develop ways to measure the concentrations of those ingredients after they’ve been kept at different temperatures, humidities and light conditions.

Ultimately, it’s about companies being more proactive in their ingredient formulation and what they are promising to shoppers.

“It’s in nobody’s best interests to be giving consumers products that don’t work,” he said.