Cosmetics. Most of us use them. Whether its makeup, hair products, face or body creams, you name it, most of us use at least one on a daily basis. But, and let’s be honest, how many of us actually note down the month we opened them and go through our cosmetics monthly to check which ones are “out of date” ? How many of us actually even notice the 6M, 12M, 24M etc lifetime indicators at the back of cosmetic products? Do some of us even know what 6M, for example, stands for? And if you roughly guess that your favorite cream or mascara is in principle expired wouldn’t you use it anyway? How many times did you say “Ah it will be fine”?
Cosmetics, like any other product, have an expiration date. Instead of your standard date/month/year (or other formats depending in which country you live in) expiration date found in most products, cosmetics have their own format. This is usually a number next to the capital letter M. For example, 6M would imply that this product has a 6 month lifetime, 12M = 12 months, 24M = 24 months etc.
The reason behind this format is that cosmetic expiration dates, unlike other products, do not need to be as accurate, to a specific date, for several reasons such as:
(a) they are not eaten (except from those body butters that smell so nice right?),
(b) they usually contain stabilizer compounds that keep them fairly stable for a while and
(c) until they are opened, they are bacteria free and sealed from environmental decay (such as light, moisture etc).
As a result, the expiration clock starts ticking when you as the consumer open and/or start using the product and not so much when the product was produced or purchased. Bear in mind though that obviously there are limits to this, if you keep a product for a while (months or years depending on the product) at some point it will decompose on its own, even when sealed, as the formulation will get destabilized at some point. That point however, is usually longer than the time it takes for environmental, biological factors and usage to destroy the product. Thankfully, if a product decomposes on its own you probably didn’t like it anyway or you have too many, otherwise you would have used it already. So no worries!
However, confusion comes when some products are sold sealed and some not. Technically, if you buy a product that did not have a seal, its expiration date might not be as accurate, as the product would have already been exposed to environmental factors such as air for example. Let’s be optimistic and believe that those products and their formulation are usually air stable and therefore do not need to be sealed. But bear in mind, that might not be the case for all of them. If you have a choice of two products where one brand sells them sealed and the other doesn’t, the choice is clear. Let’s not forget that this way you also know that no one touched or used it already!
Strangely, there aren’t many scientific studies on expired cosmetics and their effect. Perhaps because it is expected that we wouldn’t use them past their time. There is however, an interesting study by the Society of Cosmetic Scientists based on the habits of 44 (18-28 years old) University students, investigating the use of expired make-up and their microbiological contamination.  Turns out, 97.9% of them (that’s 43 out of 44 students!) have used or been using expired make-up with mascaras being the most common.  The microbological analysis of 40 mascaras collected from the students revealed the presence of bacteria and fungi!  About 79% of the samples contained Staphylococcus aureus and 13% Pseudomonas aeruginosa.  Both these organisms can cause skin irritations and other more serious health issues such as food poisoning, organ infections etc when ingested which think about it, it’s not that difficult to do considering our make-up is on our face and mouth which we use and touch when eating or drinking.
One might argue however, that most of the bacteria species found in cosmetics are due to our natural bacterial present already on our body and skin. That is true. However, if this bacterial thrives and replicates inside the cosmetic products the imbalance of their numbers to our natural flora can cause health problems.
Contact dermatitis is one of the most common infections occurred with 5% of all reported dermatitis between 1977 – 1983 being due to the use of expired make-up. [1, 2] Obviously we are now using a lot more cosmetics than back then and so the number for today is probably higher. There is one study in 2013 that reports commonly occurring side effects, from the use of cosmetics, in descending order: acne, allergy, skin burns, inflammation, itching, infection, eye and nasal irritation.  However, it is not clear whether these side effects are due to, or enhanced by, the presence of organisms rising from improper use.
The Society of Cosmetic Scientists concluded that effects such as dermatitis rise for several reasons including: [1, 4]
(a) individual susceptibility (how sensitive your skin is, how strong your immune system is etc),
(b) incorrect handling of the products,
(c) poor preservation (unstable formulations but also incorrect storing),
(d) use of products after their expiration date,
(e) sharing of cosmetics leading to microbiological contamination as each individual has a specific organism flora on their skin which might be harmful to someone else and
(f) poor handling during manufacturing or lack of good, or any, product sealing.
Incorrect storage is also a very interesting point which is now more relevant than ever. As we are in summer months bear in mind that, if you are lucky enough to be living in a hot place (30oC+), it might be a good idea to store your cosmetics in the fridge. This is a good idea not only to avoid sweating of products (you must have noticed your lipsticks sweating at some point) leading to imbalance of the formulation and possible decomposition of the compounds contained, but also thriving of some organisms such as bacteria which reproduce faster at slightly elevated temperatures (to a limit obviously they start dying from roughly 50 oC+ and above depending on the organism). Additionally, a lot of us tend to keep our cosmetics in the bathroom which is actually a very harsh environment. Bathrooms are damp places which also favor the growth and development of organisms like fungi and bacteria. 
Eye products, such as mascaras, but not only (eye liners especially liquid ones etc), require specific attention as they are the ones used closer to the eyes which are very sensitive areas and provide an easy way for organisms to enter our system. Aqueous based formulations, particularly, are linked to higher risk because, well you guessed it, water helps organisms grow. [1, 6] If you are wearing contact lenses or have a compromised immune system due to other health reasons, then you are obviously at higher risk.
As a side note, don’t forget also the silent offenders, things that might not fall exactly under the cosmetic category but are involved in the contamination process like for example your beauty blender, brushes, brush cleaners, make-up bag, eyelash curler etc. Such items, especially the spongy ones like the beauty blender, have a favourable substrate for bacteria to grow on. Never forget to wash your brushes deeply at least once a week with a daily quick clean between. Brush sprays that contain alcohol are excellent for daily quick cleans, as alcohol can kill bacteria and it evaporates quickly leaving your brush or beauty blender dry, almost instantly. For deeper cleans look for products that will soften and condition your brushes as well, to extend their lifetime and function.
Cleaning your brushes daily is not only beneficial for bacteria control but also helps with applying your make-up more smoothly. Not only because your skin will be free of breakouts but also because the brush, for example, will have less product dried on it and will therefore, apply more smoothly. So it’s a win-win!
Of course, adverse effects will not happen every time. In this particular study, which granted is on a small sample size of only 44 people, the participants reported no effects 70.5% of the time.  The remaining, reported adverse effects by the use of out of date make-up including tearing, erythema (reddening of skin), itchiness, irritation and allergies with tearing being the most common at 36.4%.  So just because your out of date mascara was ok yesterday doesn’t mean it won’t make you tear up tomorrow!
In the same study, 61.4% of the students admitted to sharing make-up, even if it was just with family members whereas 68.2% of them admitted to not removing make-up before going to bed. [1, 3] This would also contribute to skin irritation and breakouts and a not so smooth make-up application the day after! Most participants said they would discard make-up products after 1 year of use (clearly not?!) and determined the ideal period of usage to be 3 months. [1, 4] I would agree with that. Less than 3 months, would make things very expensive and more than that, products will become bacteria heavens and would have also lost their function. About two thirds of the students admitted to be using mascaras for longer than 6 months and eye make-up such us eye liners and eye shadows for longer than 2 years.  How often do you replace your eye shadow palettes? Well…
Interestingly a fair amount of students had make-up that was already expired when purchased (34.1% more than a year, 13.6% more than 6 months and 13.6% more than 3 months).  This raises a lot of questions! Including that these numbers don’t add up. Maybe a typo in their publication or is the rest of the percentage the number of products that wasn’t expired (still doesn’t add up)? Not clear. Do beauty companies or shops sell out of date products? Do students or others with limited cash flow purchase them because they are supposedly cheaper? Do students purchase from non-official places? Do they trade between them? A lot of questions.
Anyhow, from all the expired make-up products 86% were eye products, 22.7% lipsticks or glosses and 6.8% foundations.  So perhaps it is a good idea to inspect your cosmetic collection for at least these three offenders. Interestingly, 95.5% of the participants had at least one make-up product where the date of expiration was not visible either because it rubbed off or because it was never printed on the product to begin with!  This information is easily lost, especially depending on which country you are in or bought the product from, some countries allow this information to be printed on the secondary packaging (the outer box for example) and not on the primary one (the actual cosmetic).
Throwing away expired cosmetics is not just about germ control or even “germ phobia”. If you are interested in enhancing your physical assets, hence using cosmetics, then you definitely don’t want any negative interference, even if it is as small as a breakout. Expired products, even if they were somehow germ free, will also behave and apply differently. Mascaras will slowly dry out and leave black bits on your lashes, eye liners will get sticky and not apply as smoothly, foundation will probably give you a cakey or oily face etc. Don’t risk it even if it’s just a pimple and nothing more serious, it’s not worth it. There is something cathartic about going through your things and having a little spring clean, whether its cosmetic or other stuff, so include this in your decluttering processes every 6 months, especially when the year season and by default, the environmental conditions change. Who doesn’t like going through their cosmetic collection? Perhaps throwing away some old cosmetics is a good opportunity to buy some new ones? A lot of brands are releasing summer collections this time of the year. Motivation right there!
With all this information at hand, here’s the dos and don’ts for the correct use of cosmetics according to the Society of Cosmetic Scientists and the FDA [1, 7]:
- Store cosmetics in a dry and cool environment (unless stated otherwise) below 30oC (86 oF)
- Do not share cosmetics, use applicators that you can discard if you have to share.
- Do not use old applicators in new products.
- Do not moisten cosmetics.
- Do not use cosmetics that have changed physical state (dried out, changed colour, smell, texture etc)
- Do not use out of date cosmetics especially the eye related products.
- Insert your contact lenses before cosmetic application.
- Replace your cosmetics after a serious breakout or bacterial infection.
- Test new cosmetics at least 24 hours prior of main usage (at the back of your hand or under your armpit) for allergies.
- See a medical doctor if any adverse effects occur including tearing, redness, itchiness, burning sensation etc.
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