For years now, the awareness of the danger of exposing oneself to the rays of the sun without protection has permeated most of society. According to the Association Against Cancer , 80% use sunscreen when going to the beach , 50% apply it when they practice outdoor sports in summer and 42% use products with protection daily, such as creams moisturizers or makeup.
Despite this, there are still doubts that we all have about how to properly use a sunscreen . One of them is how long you can use one of these products after opening it. Can I reuse a cream from last year ? How do I know if my cream has ‘expired’? What happens to a protector when it expires?
Imagine that the sun cream you just bought is a toaster: it has some instructionsfor use that you probably will not read because, total, you know how it works. Well, reconsider it. Each sunscreen has its particularities and the manufacturer will have entered in that part of the label the specific indications .
From the ingredients of the cream, to the most appropriate reapplication period until the compatibility with water or sweat, for example, will appear there detailed. It is especially useful if you have an allergy or you are going to use the cream for sports, for example.
Minimum duration date
Now imagine that the same cream is a food. This date would be equivalent to the preferential consumption date , the minimum time in which the manufacturer guarantees all the unopened properties of the product.
Period once opened
This is in this case the information that most interests us: how long once opened we can continue using our sunscreen. This information is indicated next to the acronym PAO (period after opening) and is indicated by the symbol of an open jar containing a number next to the letter M.
That number is the months that the product maintains its properties once opened. In most cases, the sun creams are marked as “12M” , that is, they can be used 12 months once opened.
What does a sunscreen wear?
To understand this, it is useful to imagine sun creams as if they were sauces in the kitchen . Its ingredients are of different types. The most important are the compounds that absorb solar radiation to prevent it from damaging our skin, called filters.
The filters can be physical or chemical , and each has its advantages and disadvantages. Physicists are more stable over time, but they are more dehydrating and leave a white trace on the skin when applied. The chemicals allow to create creams with moisturizing effect and do not leave that trace, but in exchange they last less time. It is common for the highest quality sunscreens to carry a mixture of both.
In addition to the filters, the sunscreens carry other compounds that act providing the mixture with stability, a pleasant texture or aroma. The final recipe results in the product as it is when we buy it.
What happens to a cream over time?
But with the passage of time, these components begin to degrade , just as a sauce would. The first effect is usually perceived in its texture. The emulsifiers are degraded and the oily part is separated from the water, with a clear liquid appearing on a more white and thick liquid. This can be resolved in a timely manner by shaking the can of cream well and applying it immediately before the two layers separate again.
The stability of sunscreens is another thing that is compromised over time, and this will decrease the effectiveness (the protection factor or FP) of a cream. This should be taken into account because with an old protector applications should be made more often than with a new cream.
Tips to keep a sunscreen
Let’s go back to the analogy with a sauce: the more adequate the conservation conditions of a sunscreen, the longer it will maintain its qualities. This means keeping the boat in a cool, dry place .
But we must bear in mind that this is not always possible , because sunscreen is usually needed precisely in situations of heat and humidity, such as the beach and the pool. Exposing it for hours in sunlight, sometimes inside a car, having it in contact with the sand … All these things cause the degradation of the cream to accelerate.
On the other hand, it is advisable to take into account the quality of the cream and the shape of the bottle that contains it . A spray protector that is hardly in contact with the air will not be the same as a badly closed boat that is in continuous contact.
In any case, and when in doubt follow the manufacturer’s recommendations, opt for smaller boats and acquire a new protector if the previous one had a hectic beach life last year . Do not play with the health of your skin.