How long does it take for sunscreen spray to expire after opening? Can sunscreen spray still be used one year after opening?

I believe many people have had this experience with sunscreen spray. They opened a bottle of sunscreen spray at the end of this summer, and then continued to use it when the weather was hot next year. Will it still work? Let’s take a look!

How long does it take for sunscreen spray to expire after opening?

One year.
The shelf life of sunscreen products is generally three to five years, but they must be used up within one year after opening. The same goes for sunscreen spray. If the sunscreen spray is not used up within a year after opening, its texture and ingredients may oxidize and change, which will greatly reduce its sun protection ability. Therefore, whether it is sunscreen spray or sunscreen, it must be used up as soon as possible after opening, and it should be stored in a cool and dry place at ordinary times to avoid exposure to sunlight.

Can sunscreen spray still be used one year after opening?

Sunscreen may or may not be usable after being opened for one year, but it is recommended not to use it. Here are the reasons:

1. Reasons for shelf life. The shelf life of general sunscreen is two to three years. After opening, the shelf life will definitely be shortened. It is generally recommended to use it within six months. After opening, the product will come into contact with air and hands, which will contain moisture, bacteria, oil, etc., making it relatively easy for bacteria to grow on it, so it is recommended to be used within six months. Cosmetics manufacturers usually conduct anti-corruption challenge tests before leaving the factory. Generally speaking, some bacteria are not so easy to grow. However, with the frequency of use, humidity and moisture in the air and other conditions, it will be relatively easy for bacteria to grow over time.

2. Reduction of sun protection ability. The main function of sunscreen is to protect against the sun. In sunscreen, the main function of sun protection is sunscreen, which can be divided into physical sunscreen and chemical sunscreen. Physical sunscreens are mainly composed of titanium dioxide and zinc oxide; there are several types of chemical sunscreens, all of which are irritating.

Currently on the market, in order to achieve better skin feel, cost, and sun protection ability, general sunscreens are used together with physical sunscreens and chemical sunscreens. For chemical sunscreens, the SPF value will definitely decrease over time, which means that the sun protection ability will decrease. How much the chemical sunscreen can reduce the SPF value has a lot to do with the formula system and the combination of cosmetic raw materials used. However, there is no way to avoid a reduction in SPF value.

There are also some cosmetics manufacturers whose sunscreens have been on the shelves for too long (half a year or a year). When they are sampled by the Food and Drug Administration, it is found that the actual SPF value does not reach the labeled SPF value. Sometimes, it is even exaggerated to be only half of the SPF value. This is mainly because the chemical sunscreens gradually degrade and their sun protection ability is reduced.

suggestion:

1. Do not use sunscreen within one year after opening.

2. When purchasing sunscreen products, give priority to those with a newer shelf life.

These indicators are important

1. Stability of sunscreen

"Sunscreen" is the core ingredient of a sunscreen product and directly determines the sun protection ability of this product.

Sunscreens can be divided into two categories: physical sunscreens and chemical sunscreens.

Physical sunscreens: There are very few types, the most common ones are titanium dioxide and zinc oxide. These two sunscreens are highly inert and stable, and can remain stable even in extreme exposure environments.

Chemical sunscreens: After absorbing ultraviolet rays, the electrons in the molecules jump from low-energy orbits to high-energy orbits, achieving the purpose of sun protection. It should be noted that chemical sunscreens will only decompose easily after being exposed to sunlight, not when exposed to oxygen. We do not expose sunscreen products to high temperatures or sunlight in our daily use. We cover the lid immediately after opening. This way, the sunscreen can remain stable for a long time and its sun protection ability will not decrease.

2. Stability of the paste

The stability of sunscreen paste also has a great impact on the product's sun protection ability. If the paste is unstable, the sunscreen will be delaminated or precipitated, which will directly affect the film-forming property of the sunscreen and greatly reduce its sun protection ability. If the above situation occurs, it means that the stability of the paste has been destroyed and it can no longer be used.

3. Bacterial contamination

One year after opening, the bacteria and fungi of sunscreen will not exceed the national standards. Any cosmetics will have preservation measures, most of which are preserved by preservatives. Preservative ability is one of the factors that must be considered when designing a formula. If you don't consider the irritation to the skin, the existing preservation technology is already very complete. As long as you put the lid back on immediately after opening and don't leave the paste exposed to the air for a long time, it can be stored for a year without any problems. Microorganisms generally do not exceed the standard.

Analyzing the shelf life of sunscreen products

We start from four aspects: 1. The stability of sunscreen; 2. The stability of sunscreen paste after opening; 3. The interference of microorganisms on sunscreen. 4. Stability of other ingredients.

1. Stability of sunscreen

Sunscreen can be divided into physical sunscreen and chemical sunscreen according to the principle of sun protection.

1) Let’s first talk about the stability of physical sunscreens. Common physical sunscreens include zinc oxide and titanium dioxide, which are widely used in sunscreen products.

(1) Zinc oxide is an oxide of zinc. It is insoluble in water but soluble in acids and strong alkalis. Its melting point is 1975°C and its boiling point is 2360°C. It can be seen that it is extremely stable.

(2) Titanium dioxide is a material with low hygroscopicity and excellent thermal stability, which shows that its stability is also very high.

In other words, both physical sunscreens are highly stable and can remain stable even under extremely high temperatures. They are not easily decomposed, oxidized, or denatured. Therefore, after opening, physical sunscreens will not deteriorate easily, thereby reducing the sun protection effect.

2) Let’s talk about the stability of chemical sunscreens. Common chemical sunscreens include benzophenone, ethyl salicylate, homosalate, cinoxate, and mesalamine. Its sun protection mechanism is that after the chemical sunscreen absorbs ultraviolet rays, its electrons jump from low-energy orbits to high-energy orbits, thereby achieving the purpose of sun protection and ending its "life". This great chemical sunscreen has a drawback, however, which is that it is not very photostable under long-term sunlight exposure.

It is important to emphasize here that chemical sunscreens will only decompose and become ineffective under long-term exposure to sunlight, rather than being oxidized. Therefore, as long as they are not exposed to high temperature and light for a long time, chemical sunscreens will not be decomposed after opening.

2. Stability of sunscreen cream after opening

The stability of sunscreen cream is very important in any sunscreen system and directly affects the sunscreen effect. In fact, as long as the sunscreen you buy is produced and tested by a regular manufacturer according to regular processes, and as long as the paste does not show stratification, precipitation, water-oil separation, etc., there will be no problems with the paste.

3. Microbial interference with sunscreen

Everyone knows that sunscreens produced by regular manufacturers undergo a series of microbial tests before production. But after a year of opening the sunscreen, are the microorganisms in the sunscreen exceeding the standard? This is inseparable from the anti-corrosion ability of its anti-corrosion system. If the cap of sunscreen is tightened one year after opening and placed in a cool, dry and clean place, it generally will not breed bacteria.

4. Stability of other ingredients

In addition to sunscreens and preservatives, sunscreen also contains moisturizers, emollients, antioxidants and other ingredients. In fact, the amount of these ingredients added to the formula is basically less than 1%. In addition, there are strong enough preservatives in the formula. After one year of opening, if the storage environment is acceptable, it is very stable and has no effect on the sun protection effect.

5. Determine the shelf life based on the product packaging label

The outer packaging of cosmetics all have logos like the one above. Taking the above picture as an example, the shelf life of the products after opening is six months and twelve months respectively. By the same token, you can look at the logo on the outer packaging of your sunscreen to determine whether you can continue to use it.

To sum up, if the sunscreen has been opened for one year and is produced by a regular manufacturer (based on the product registration information provided by the State Food and Drug Administration), you can continue to use it as long as it is not exposed to high temperature and sunlight for a long time. In other words, the correct way to store sunscreen is to seal the lid tightly and keep it in a cool, dry, clean and hygienic environment. Even if it is opened for a year, it is still safe to use again!