Water resistance is an important consideration for sunscreen products designed to be worn while swimming, exercising or spending extended time outdoors.
But a sunscreen cannot simply be described as water resistant because the formula is designed to stay on the skin. The claim needs to be supported by appropriate testing, and the requirements can differ depending on where the product will be sold.
For brands developing sunscreen, understanding water resistance testing early can help shape the product brief, testing plan and claims before packaging and artwork are finalised.
What Does Water Resistance Mean in Sunscreen?
A water-resistant sunscreen is one that has demonstrated an appropriate level of SPF protection after being exposed to water under defined test conditions.
It does not mean the sunscreen is waterproof or that it will remain on the skin indefinitely.
During water resistance testing, sunscreen is applied to test subjects and the treated skin is exposed to controlled periods of water immersion. SPF is then assessed following the required water exposure.
The results are used to determine whether the product can support the intended water-resistance claim.
This distinction is important for brands. A high SPF result before water exposure does not automatically mean the product can make a water-resistance claim. The product needs to be tested using the method required for the intended market.
What Do 40 and 80 Minutes of Water Resistance Mean?
The terms 40 minutes and 80 minutes are commonly associated with sunscreen water-resistance testing, particularly in the United States.
They refer to the amount of water immersion the sunscreen has undergone during testing before its SPF is assessed.
An 80-minute water-resistant sunscreen has therefore been tested following a longer total period of water immersion than a product carrying a 40-minute claim.
This does not mean someone can apply an 80-minute sunscreen and ignore reapplication instructions for 80 minutes under every circumstance.
Activities such as towel drying can remove sunscreen, and consumers still need to follow the directions provided on the label.
40-Minute Water Resistance
Under the FDA testing framework, a 40-minute water-resistance claim involves two 20-minute periods of water immersion, with a drying period between them.
After the required immersion and drying process has been completed, the sunscreen’s SPF is assessed.
If the product meets the applicable requirements, its label can state that it is water resistant for 40 minutes.
80-Minute Water Resistance
For an 80-minute claim, the water-immersion process is extended.
The FDA method uses four 20-minute periods of water immersion, again with defined drying periods between them.
The SPF is then assessed following the full 80 minutes of water exposure.
For brands, the important point is that 40 and 80 minutes are tested claims. They are not simply descriptions chosen for the packaging.
How Is Sunscreen Water Resistance Tested?
Water resistance testing is carried out under controlled conditions so that the product can be assessed consistently.
The exact procedure depends on the standard and market being used, but the process generally follows the same basic principle:
- The sunscreen is applied. A defined amount of the product is applied to the test area according to the relevant test method.
- The product is allowed to settle on the skin. The test method specifies how the product is applied and the time allowed before water exposure.
- The test area is immersed in water. Subjects complete the required periods of controlled water immersion.
- Drying periods are included. Depending on the method, periods outside the water separate the immersion cycles.
- SPF is assessed following water exposure. Testing determines the level of SPF protection demonstrated after the required immersion period.
- The result is reviewed against the intended claim. The results are assessed according to the standard and market requirements that apply to the product.
The purpose is to create a controlled way of assessing how the sunscreen performs after water exposure.
Real-world conditions will naturally vary, which is why consumers still need to follow the application and reapplication directions on the finished product.
What Happens During the Water Immersion Stage?
The water immersion part of the test is controlled rather than simply asking a participant to swim normally.
The relevant method sets requirements for how the water exposure takes place, including the immersion periods and conditions used during testing.
For FDA water-resistance testing, the process involves 20-minute periods of moderate activity in water followed by defined periods out of the water. The number of cycles depends on whether the product is being tested for a 40 or 80-minute claim.
International testing methods also provide standardised approaches to water immersion so that water resistance can be assessed alongside SPF testing.
For brands, the detailed testing procedure will usually be managed by the specialist sunscreen testing facility. The more useful question during development is which claim the product is being designed to support and which testing pathway applies to the intended market.
Which ISO Standards Apply to Water Resistance Testing?
International standards provide recognised methods for assessing sunscreen performance.
ISO 16217:2020 sets out a water-immersion procedure used when determining the water resistance of sunscreen products. It is designed to be used alongside the SPF testing method in ISO 24444.
ISO 18861:2020 provides a method for evaluating the percentage of water resistance. It compares the SPF measured before water immersion with the SPF measured after the defined water exposure.
These standards provide testing methods. The claim a brand can ultimately make still depends on the requirements of the market where the sunscreen will be sold.
That distinction matters because Australia, the United States and other markets do not necessarily use water-resistance claims in exactly the same way.
Water Resistance Requirements in Australia
Australia uses the Australian/New Zealand Sunscreen Standard, AS/NZS 2604:2021, for new sunscreen products.
The standard incorporates international testing methods but also includes Australian-specific requirements.
One important difference is that Australian water-resistance claims are not limited to the 40 and 80-minute wording commonly seen in the United States.
Under the current Australian standard, the maximum water-resistance duration that can be claimed is linked to the SPF of the product.
A sunscreen with an SPF of 30 or above may support a water-resistance claim of up to four hours where the appropriate testing requirements are met. Products with lower SPF levels have lower maximum claim durations.
This is why a brand developing sunscreen for Australia should not choose its desired water-resistance claim based purely on what it has seen on products in another market.
The intended SPF, testing results and requirements of the Australian standard all need to be considered.
For therapeutic sunscreens, the sponsor is responsible for holding appropriate evidence to support the water-resistance claim made for the product.
Water Resistance Requirements in the United States
In the United States, sunscreens are regulated by the FDA as over-the-counter drug products.
Where a brand wants to make a water-resistance claim, the product must meet the FDA’s applicable water-resistance testing requirements.
The recognised claims are:
Water Resistant (40 minutes) and Water Resistant (80 minutes).
The label also needs to provide the applicable reapplication directions.
Terms such as waterproof, sweatproof and sunblock are not permitted under the FDA sunscreen framework because they can give consumers the impression that the product provides a level or duration of protection that has not been demonstrated.
For Australian brands considering the US market, this is another reason claims and packaging should be reviewed for the intended region rather than simply carrying Australian wording across to the US product.
Does a Higher SPF Mean Better Water Resistance?
No. SPF and water resistance describe different aspects of sunscreen performance.
SPF relates to the level of sun protection demonstrated by the product under the applicable SPF test.
Water resistance considers how the product’s SPF performs following a defined period of water immersion.
A high-SPF sunscreen therefore does not automatically have a high level of water resistance.
If a water-resistance claim is planned, the product needs to go through the relevant testing pathway.
When Should Water Resistance Be Considered During SPF Development?
Ideally, before the formulation has been finalised.
If a brand wants to develop a sunscreen for sport, swimming, outdoor activity or another use where water resistance is important, that should form part of the original product brief.
The formulation team can then consider the intended SPF, desired product experience and water-resistance goal during development.
Testing should also be factored into the project timeline. If the product does not support the intended claim, further formulation work and repeat testing may be required.
It is also worth confirming the intended markets early. A product being developed only for Australia may follow a different claim and testing strategy from one intended for both Australia and the United States.
Water Resistance Testing and Delta
Delta works with skincare and personal care brands across SPF formulation development and commercial manufacturing.
When water resistance is part of the product brief, it can be considered during formulation development alongside the intended SPF, product format, claims and target market.
Depending on the project, Delta can support formulation development, lab samples, stability testing, manufacturing scale-up and planning for the required external SPF and water-resistance testing.
Specialist SPF and water-resistance testing is completed through appropriate testing facilities, with the required pathway determined by the product and intended market.
Discussing the water-resistance goal early gives the brand and formulation team a clearer understanding of what the finished product is intended to achieve before claims and packaging are locked in.
FAQ: SPF Water Resistance Testing
What does water resistant SPF mean?
It means the sunscreen has undergone testing to assess its SPF following a defined period of water exposure. The exact claim and testing requirements depend on the market.
What does 80 minutes water resistant mean?
In the United States, an 80-minute water-resistance claim means the sunscreen has been tested after a total of 80 minutes of water immersion using the applicable FDA procedure. It does not mean the sunscreen is waterproof.
What is the difference between 40 and 80-minute sunscreen?
The difference is the amount of water immersion completed during the required test. Under the FDA method, a 40-minute claim involves two 20-minute immersion periods, while an 80-minute claim involves four.
Can sunscreen be labelled waterproof?
No. Sunscreens eventually wear or wash off. In the United States, terms such as waterproof and sweatproof are not permitted sunscreen claims. Australian guidance also does not accept waterproof or sweatproof wording for sunscreens.
How long can sunscreen be labelled water resistant in Australia?
Under the current Australian standard, the maximum claim depends on the product’s SPF and the results of the required testing. Products with SPF 30 or above may support water-resistance claims of up to four hours where the applicable requirements are met.
Is water resistance testing the same as SPF testing?
They are connected, but they are not the same claim. Water-resistance testing assesses sunscreen performance following defined water exposure, while SPF testing establishes the product’s sun protection factor according to the relevant method.
Does every sunscreen need water resistance testing?
Not every sunscreen needs to make a water-resistance claim. If a brand wants to claim that the product is water resistant, the claim needs to be supported by the testing required for the intended market.
Developing a Water-Resistant SPF?
If water resistance is part of your sunscreen concept, it is worth discussing the intended claim and market while the product is still being developed.
Delta works with brands across SPF formulation development, scale-up and commercial manufacturing, with external testing requirements considered as part of the development pathway.
Speak to Delta
Talk to Delta about your SPF product, water-resistance goals and commercial manufacturing requirements.