The science behind UPF clothing: how it protects your skin

As conversations around skin health evolve and sun exposure becomes a growing concern, one innovation stands out for its simplicity and effectiveness: UPF 50+ clothing. Designed to offer real protection against ultraviolet radiation, UPF garments have become an essential part of any modern wardrobe, especially for those who enjoy spending time outdoors without putting their skin at risk.

But how does UPF clothing actually work? What makes it different from regular clothing? And how do we know it's truly protecting us?

Let’s dive into the science behind anti-UV textiles, and explore how UPF 50+ fabrics shield your skin from damage while allowing you to enjoy the sun with confidence and freedom.

Understanding the enemy: what is UV radiation?

To fully appreciate the role of UPF clothing, it helps to understand the nature of what it protects us from.

Ultraviolet radiation, commonly known as UV rays, is emitted by the sun and comes in three forms: UVA, UVB, and UVC. UVC rays are absorbed by the ozone layer and don’t reach the earth’s surface, but UVA and UVB rays do, and they are responsible for most of the damage to our skin.

UVA rays penetrate deeper into the skin, contributing to premature aging, loss of elasticity, and pigmentation issues. UVB rays are shorter and more intense, responsible for sunburns and directly damaging the skin’s DNA, which increases the risk of skin cancer.

While sunscreen plays a critical role in preventing sunburn and skin damage, it has its limits. That’s where UPF 50+ clothing comes in: a wearable shield that blocks out the majority of harmful rays before they even touch your skin.

What does UPF really mean?

UPF stands for ultraviolet protection factor, and it’s a standard used to measure how much UV radiation a fabric allows to reach the skin.

A rating of UPF 50+ means the fabric blocks more than 98 percent of UV rays, allowing less than two percent to pass through. In comparison, a typical white cotton t-shirt offers a UPF of only around 5 to 8, which is far from sufficient for extended sun exposure.

Unlike SPF, which applies to skincare products and measures how long you can stay in the sun before burning, UPF relates strictly to textiles. It doesn’t depend on time but on the percentage of rays blocked. That makes UPF clothing a reliable and stable form of sun protection, especially when reapplying sunscreen is difficult or inconvenient.

All Juillet Juillet’s swimsuits are made from certified UPF 50+ fabric, tested under strict standards to ensure optimal protection even after contact with water, salt, or chlorine.

What makes a fabric UV-protective?

Not all fabrics are created equal when it comes to UV defense. The UV-blocking performance of a garment depends on a mix of factors, including material, weave, color, treatments, and even how the garment fits on the body.

First, the density of the weave plays a critical role. Tightly woven fabrics have fewer gaps between threads, which means fewer opportunities for UV rays to pass through. While lightweight, loose-weave cotton may feel comfortable, it usually doesn’t offer sufficient protection without additional treatment.

Synthetic fibers like polyester and nylon are commonly used in UPF 50+ swimwear because their structure allows for tighter weaves and better resistance to water and sunlight. These fibers also tend to reflect or absorb UV rays more efficiently than natural fibers.

Color matters, too. Darker shades absorb more UV radiation, preventing it from reaching the skin underneath. However, at Juillet Juillet, we’ve worked extensively to ensure that even our light and pastel tones provide the same certified UPF 50+ protection, so that your style doesn’t have to compromise your safety.

Another layer of defense comes from specialized treatments applied during the fabric’s manufacturing. These may include UV-absorbing or reflecting agents, which are bonded to the fibers. Some fabrics also incorporate microscopic particles of zinc oxide or titanium dioxide, the same ingredients found in physical sunscreens, to scatter UV rays and enhance sun protection even further.

Why UPF 50+ clothing is a game-changer

Wearing UPF 50+ swimwear isn’t just about avoiding sunburn. It’s about minimizing the cumulative, long-term damage that often goes unnoticed until it’s too late.

Unlike sunscreen, which must be reapplied every two hours and often degrades with sweat and water, UPF clothing stays effective as long as you wear it. That’s especially useful for families, beachgoers, hikers, or anyone who wants to enjoy the outdoors without constantly stopping to reapply.

For children and babies, UPF clothing is invaluable. Their skin is thinner, more sensitive, and more susceptible to damage. A long sleeve anti-UV swimsuit covers the areas most exposed—shoulders, arms, chest, and upper back—and makes sun safety much more manageable for parents.

Adults, too, benefit from UPF garments that combine coverage, comfort, and style. Whether it’s a rashguard, or high-neck top, the goal is to protect without overheating, restrictiveness, or sacrificing aesthetics. Our women’s collection includes elegant long sleeve swimsuits, bikini sets, and coverage-enhancing one-pieces, all engineered for movement, durability, and confidence.

How to maintain UPF protection over time

The good news is that UPF protection is durable, but it’s not immune to wear and tear. Like any fabric, UV-blocking materials can degrade over time with repeated washing, sun exposure, and friction.

To preserve the integrity of your anti-UV maillots de bain, follow these best practices:

• Rinse with cool water after swimming to remove salt, chlorine, or sunscreen

• Avoid wringing or twisting the fabric

• Let your swimsuit air dry in the shade rather than direct sunlight

• Avoid bleach and harsh detergents

When well cared for, UPF garments will keep their protective properties season after season, making them a long-term investment in your skin health.

UPF clothing and the future of sun protection

As we become more informed about the dangers of UV radiation and more conscious of the importance of preventive care, UPF 50+ clothing is becoming a new standard, not just a niche solution. It complements, but does not replace, other forms of protection, such as sunscreen, sunglasses, and hats.

At Juillet Juillet, our mission is to make sun-safe living desirable and easy. Every detail of our designs is carefully thought out, from coverage to cut, comfort to materials, so that your skin is protected, your movements are free, and your beach days are beautiful.

UPF clothing is more than a trend. It’s the next step in sustainable sun protection, a solution rooted in science and driven by care.

Ready to protect your skin with style?

If you're looking to build a wardrobe that keeps your skin safe without compromising on design, explore our curated selection of UPF 50+ swimsuits. Our pieces are crafted for women, kids, and babies with soft fabrics, elegant shapes, and long-lasting protection.

Whether you're swimming, playing, traveling, or relaxing, there's no need to choose between fashion and function. With Juillet Juillet, you can have both.