What Is Rash Guard Swimwear? – Knix

You may be thinking to yourself: what is rash guard swimwear, exactly? A rash guard (also sometimes called a rash vest, rashie, or swim shirt) is an athletic shirt made of spandex and nylon or polyester. It is designed to be worn in the water, either on its own or (more usually) over a bathing suit or bikini top.

Traditional rash guards started as a piece of surfing apparel. When it’s too warm for a wetsuit, the rash guard will protect a surfer’s body from the friction caused by rubbing against a surfboard and the waxy residue on a surfboard.

While rash guards are still worn for surfing and other water sports, they have also found their way into more mainstream swimwear. This is because they offer a myriad of benefits that many of us enjoy, whether we’re very active in the water or not.

Let’s take a deep dive into rash guard swimwear!

Swim Shirts, Sun Shirts or Rash Guards: What’s the Difference?

Swim shirts are a little more loose-fitting than rash guard shirts and are not designed to be submerged in water. Think of a swim shirt as a garment with the ‘look’ of a rash guard with a more loose fit. They're really designed to be worn on land. 

This doesn’t mean swim shirts are not useful, too: When you emerge from the water or if you feel a chill on the beach, a swim shirt can offer a protective layer between your skin and the sun's harmful rays and other elements.

However, because it is more loose-fitting, it would have too much drag in the water. It may also lack the quick-drying properties that you should look for in a true rash guard.

A sun shirt is any top that offers UV protection but may be styled to look like a regular t-shirt, rather than having the traditional long-sleeved, high neck look of a rash guard.

So, Why Should I Wear a Rash Guard?  

In addition to its original protective intent for surfers, rash guards have many benefits.

Rash Guards Offer Sun Protection from UV Rays

These days, we understand the risks of sun damage a lot more than we used to. Whether you’re coming at it from a cosmetic angle and worried about premature aging, or you’re thinking about health issues like skin cancer (or a bit of both!), most of us want to protect our skin from prolonged sun exposure and harmful UV rays.

And if you’re in and out of the water all day, it can be challenging to maintain sunscreen applications. A rash guard provides a physical barrier between your skin and the sun that can supplement and support your other sun protection efforts. But material alone doesn’t protect you from harmful UV rays. 

Look for a rash guard with sun-repellent materials and properties measured by an Ultraviolet Protection Factor (UPF) rating.

They Offer Skin Protection from Chafing and Irritation

True to the rash guard's primary purpose and original intent, rash guards can also protect your skin from chafing and irritation. Even if you’re not surfing, sand and saltwater combinations can be a lot to throw at the skin, especially in combination with the sun. And if you participate in water sports, water spray can also be an irritant. 

Your rash guard offers a protective layer for sensitive skin in many scenarios.

Rash Guards Provide a Warm Layer in Cold Water

Even on a warm day, the water can be chilly. If you’re swimming in colder climes or just taking that first early morning plunge, you might want an extra protective layer to help keep you warm. 

Without going full-on wetsuit, a rash guard shirt offers another layer to keep you warm. And because it offers a lot more coverage than typical swimwear, you should retain more of your body warmth.

Protect Skin From Jellyfish and Other Critters

The sea is full of many wonders. But some of them can bite or sting. While wearing a rash guard won’t guarantee protection against every possible critter and creature, it will add a layer of protection to the wearer's skin.

Wear Rash Guards for a Sleek but Modest Look

Practical considerations aside, we love the look of a rash guard. It offers a sleek and sexy athletic look. Zippers allow you to reveal as much or as little as you like. But if you’re more modest and feel too exposed in a swimsuit, a rash guard can protect your modesty with some extra coverage while still allowing you the freedom to move in the water.

What to Look For in a Rash Guard

If you’re sold on the idea of a rash guard, here are some features you may want to look for while shopping for one:

Rash Guards Should Offer Fitted Stretch

Ever gone swimming in a baggy t-shirt? It’s not fun. Rash guards should be fitted enough that they won’t “bag out” in the water. At the same time, you don’t want them to be so tight that you feel like they’re constricting your movements or causing chafing or discomfort. 

Think of them as fitting like leggings—a snug, second-skin kind of support without any pinching or squeezing. 

Some may even offer additional compression with thicker fabric, which athletes may feel benefits their performance. And some may offer built-in support for the bust, too.

Rash Guards Should Be Made of Quick-Drying Material

Rash guards are not designed to be waterproof, so you want them to be quick-drying (or else you could get the chills wearing them in and out of the water all day).

Breathability Is Key

Obviously, you don’t want to be sweltering in your swimwear. So it’s important that your rash guard is made of breathable fabric that will allow you to stay cool.

Ultraviolet Protection Factor (UPF)

If protection from the sun is your primary motivation for buying a rash guard, it’s worth checking to make sure the one you’re looking at has an Ultraviolet Protection Factor (UPF) rating. While any additional layer will offer some degree of sun protection, clothing with a UPF is tested according to strict guidelines. Ultraviolet Protection Factors of 50 or more represent excellent protection.

It’s worth noting that UPF clothing with built-in UV protection extends beyond swimwear and rash guards. You can also find UPF t-shirts, leggings, and more.

However, it’s important to consider that you still need to wear sunscreen on the parts of your body not protected by the rash guard, including the face, hands, and legs. Pay attention to the neckline as well, and any parts of your decolletage that may be exposed to the sun when your rash guard is not fully zipped up.

Written by Jane Flanagan — Updated on March 5, 2023.

We hope you found this post informative — but remember: we’re not doctors and this post is not medical advice! While all posts are fact-checked and well researched, we always recommend you chat with your doctor about any questions or concerns you might have regarding a medical condition. We’re here to support and educate, but never with the aim of disregarding professional medical advice you’ve been given. Phew, now that that’s out of the way, you can go on living unapologetically free.