Four reasons why your sunscreen isn’t working

Wellbeing

When we’re out in the sun, we rely on high-SPF sunscreens to protect our skin from harmful UV rays. However, the effectiveness of your sunscreen might be compromised by a surprise factor: overheated skin.

Most people don’t realise that when their skin overheats, it can seriously undermine their sun protection. Even the highest SPF formulations can be rendered less effective when your skin temperature rises significantly.

As we head into the warmer months, understanding this connection between skin temperature and sunscreen efficacy could make all the difference in preventing sun damage. To help you, Ryan Porter, skincare expert at Fat Cow Skincare, explains why this happens and shares practical solutions to keep your skin properly protected.

How heat compromises your sunscreen

When skin temperature rises significantly, it triggers a cascade of reactions that can render even the most expensive, high-SPF sunscreens less effective.

Overheated skin responds by increasing sweat and oil production, Porter explains. This natural cooling mechanism unfortunately creates a problem for sunscreen. The increased moisture and oil can cause your carefully applied SPF to break down faster, slide off, or become unevenly distributed across your skin.

Research shows that sunscreen can begin to degrade faster when skin temperature rises above 35°C – a threshold easily reached during outdoor activities on warm days. This degradation happens because heat accelerates the breakdown of the active ingredients that block UV rays.

Many people become frustrated when they still tan or burn despite religious sunscreen application. Often, it’s because their skin temperature is undermining their protection efforts, says Porter.

Four everyday situations that affect sunscreen effectiveness

Four common situations can quickly raise skin temperature enough to compromise sunscreen protection.

1) Exercise and physical activity

During outdoor workouts, gardening, or playing sports, your core temperature rises rapidly. When you exercise outdoors, your skin can reach temperatures that accelerate sunscreen breakdown within just 15 to 20 minutes, Porter notes. This makes post-exercise reapplication essential, not optional.

2) Hot car journeys

Sitting in a car with the sun streaming through windows can create localised skin overheating. Many people don’t realise their arms and face can overheat dramatically during a car journey, especially when stuck in traffic. Car windows block UVB but allow UVA rays through, so you’re still at risk of damage, warns Porter.

3) Beach and pool days

The combination of direct sunlight, heat reflection from water, and minimal shade creates perfect conditions for sunscreen failure. Porter explains, At the beach, you’re dealing with multiple heat sources – direct sun, reflected rays from sand and water, and minimal airflow. Your skin temperature can spike quickly, making hourly reapplication necessary.

4) Outdoor dining and events

People often apply sunscreen before heading out to an outdoor lunch or garden party but don’t account for how quickly skin heats up when sitting in direct sunlight. That glass of cold wine might cool you down internally, but your skin surface can still overheat, Porter says.

Five ways to keep your sunscreen working effectively

Here are five tips for maintaining skin protection when temperatures rise.

1) Cool your skin before application

Apply sunscreen in a cool environment, ideally after your skin has been in the shade for at least 10 minutes, Porter advises. This allows the product to bond properly with your skin before sweat glands activate. A quick cool shower before application works wonders for sunscreen adhesion.

2) Use a two-step application method

Instead of applying one thick layer, try using two thinner layers applied about 5 minutes apart, suggests Porter. The first layer creates a base bond with your skin, while the second reinforces protection. This technique helps the sunscreen withstand heat and sweat much better than a single application.

3) Incorporate cooling products into your routine

Porter recommends using products with cooling ingredients before sunscreen application. Natural ingredients like aloe vera, cucumber extract, and peppermint can help lower skin temperature. Our tallow-based moisturisers work well under sunscreen because they help regulate skin temperature rather than trapping heat like some synthetic products.

4) Create physiological shade

Wear UPF-rated clothing and hats whenever possible, Porter recommends. The best way to prevent sunscreen breakdown is to reduce the heat load on your skin. Physical barriers like hats with wide brims don’t just block UV – they also keep your face cooler, which helps maintain sunscreen integrity on exposed areas.

5) Time your outdoor activities strategically

When planning your day, try to schedule intensive outdoor activities before 11 am or after 3 pm, Porter suggests. During these times, not only is UV radiation less intense, but ambient temperatures are typically lower too, creating better conditions for sunscreen to work properly.

Porter stresses that these strategies aren’t just about preventing sunburn – they’re about ensuring consistent protection against both immediate damage and long-term skin aging.

People tend to focus solely on SPF numbers, but in real-world conditions, application technique and skin temperature management often matter more than whether you’ve chosen SPF 30 or 50, he notes.

The cooling solution for proper protection

Understanding the relationship between skin temperature and sunscreen effectiveness explains why some people experience sunburn despite seemingly adequate protection. By incorporating cooling strategies into your sun protection routine, you can significantly enhance the performance of your sunscreen.

Most sun damage occurs not because people choose the wrong products, but because those products aren’t able to perform as designed under real-world conditions, Porter explains. Managing your skin’s temperature is a simple way to maximise protection without having to reapply constantly or stay indoors.

For those concerned about chemical sunscreen ingredients, Porter offers additional advice: Mineral sunscreens containing zinc oxide or titanium dioxide tend to be more heat-stable than some chemical filters. They create a physical barrier on the skin’s surface that’s less likely to break down when skin temperature rises.

Protect your skin from the sun

The connection between overheated skin and reduced sunscreen effectiveness is something the beauty industry rarely discusses. With UK summers continuing to bring higher temperatures, understanding this relationship becomes increasingly important for skin health. That makes cooling your skin before and during sun exposure a vital step in maintaining your UV protection.

Temperature management deserves as much attention as regular reapplication. Even the most expensive, highest-SPF sunscreen can’t work properly on overheated skin. Taking simple steps to keep skin cool means you’re not just preventing immediate sunburn but also protecting against premature aging and reducing long-term skin cancer risk.

Fat Cow Skincare is dedicated to creating natural, grass-fed tallow-based skincare products. Their offerings include tallow body creams, face creams, balms, soaps, and cleansers, all handcrafted with 100% natural ingredients. The products are enriched with essential vitamins like A, D, E, and K to nourish and rejuvenate the skin.