‘Base layer’ is one of the many camping buzzwords, so you may be wondering why they are so
important. In this article, we will cover everything you could possibly need to know about wearing a
Several research studies show that base layers are effective in helping the body retain heat. Base layers are designed to wick moisture from your body to keep you dry. To make a base layer effective, you first need to figure out if you want it for cold or moderate weather. Thicker, less breathable fabric is better for cold weather, but thinner more porous fabric is better for warm weather.
Are you ready to learn everything you could possibly need to know about base layers? In this complete guide to base layers, you’ll read about what makes a good base layer, when you should wear a base layer, how to pick the most effective base layer, and what you should think about if you plan to buy a base layer.
By the way, as an Amazon Associate, I earn when buying qualified products through links on my site.
There’s so much to know, but with this guide, you’ll be a pro! (rhyme intended).
Do Base Layers Work?
Before you go out and buy a base layer, the first thing you need to do is figure out how base layers work. Do base layers actually keep you warmer? And, do base layers actually wick moisture away from your body? Let’s answer both of those questions right off the bat.
Sweat Differences From Wearing Base Layers
When you wear a base layer it can seem like your sweat magically disappears. Do you even sweat when you wear a base layer? Does the base layer transport your sweat to another realm? What’s going on here? Well, it all has to do with moisture wicking. But what does that even mean?
When your base layer is against your skin, it has water-repelling properties that move the sweat away from your skin so that it can evaporate and get off your body. When the sweat evaporates, you stay warm and dry.
This study shows what happens when you don’t wear a moisture-wicking base layer. When you wear clothing that absorbs sweat instead of repelling it, the clothing prevents the sweat from evaporating and will leave you feeling cold and wet. When you’re trying to stay warm, this is not what you want.
Temperature Differences From Wearing Base Layers
Many people claim to be warmer with their base layer. However, base layers are not necessarily meant to keep you warm. Your middle layer is supposed to be the insulating layer, not your base layer. Base layers are meant to prevent you from being cold by moving sweat away from your body to be evaporated. You can look at the study in the section above and see what happens when you don’t wear clothing that wicks moisture–but to sum it up: you’ll be wet and cold!
Wearing a proper base layer will help you regulate your body temperature. This study, although performed on cyclists, shows the difference between body temperatures with and without a base layer. It uses thermal imaging to show the differences in body temperature before, during, and after movement.
Basically, base layers helped with body temperature regulation. And in this case, actually kept the body cool and comfortable while working out. Wild, right? Who would have thought that wearing clothing could actually keep you cool?
Which Types of Base Layers Work Best?
If you’re researching base layers, this is probably one of your key questions. While some people may swear that the material makes all the difference, that may not actually be the case according to a study done by Morrissey and Rossi (2013). If you want the base layer that works best, pay attention to the weave and thickness.
Additionally, this study found that the material didn’t make much of a difference comfort-wise. Shocked? We were too when we first read this article, so feel free to check out either of the links above for the full read.
Even though the material matters less than weave and thickness, we’ll still go through the common types of base layer materials and explore the pros and cons. But first, let’s discuss what weave and thickness are and why they matter.
When discussing weave, you can’t leave out breathability. The weave of a fabric is basically how tight each stitch is together. The wider the holes, aka, pores, the more breathable the fabric is. Similarly, the bigger the pores in a fabric, the more air will get through and vice versa.
So, when you’re looking for a base layer, you probably want a weave that’s tight together so that no air can pass through. When no air passes through, you stay warmer!
On the flip side, you may want a weave that’s more porous for the warm summer months. If you choose a weave that has high breathability (such as those fishnet base layers) more air can pass through the fabric and you’ll feel cooler.
Generally, the thicker the material the warmer it will be--as you might expect. It’s the difference between a light jacket and the big puffy coat your mom made you wear when it started getting cold in the fall.
If you want a warm thermal, go for one with thicker material, or a heavier ‘weight.’ If you want something lighter and not as warm, choose a thinner material. I have an entire section on thermal thickness and weight below, so keep reading to get all the facts!
While weave and thickness may be important to the function of a base layer, the material isn’t something to be ignored. To some people, the material means everything for comfort.
Merino wool works a little differently than other base layer materials. Instead of wicking the moisture (like we mentioned above), it relies more on water absorption. Wool will absorb the water so that you feel nice and dry. However, if you tend to sweat a lot you may start to feel a little moist after hours of wearing merino wool.
Merino wool can hold around 30 percent of its weight in water, so you’ll only feel wet once you’ve truly saturated the material. The difference is that wool will pull the moisture away from your skin. You can still feel cold in this situation so it’s not perfect.
|Comfortable/soft||Dries slower than other base layers|
|Stain and odor resistant||May shrink in the wash|
|Great temperature regulation||Moth damage if not stored well|
The most common synthetic materials are polyester, nylon, and spandex. When you’re shopping for a synthetic material-based base layer, you’ll likely see a lot of polyesters. While some people report feeling uncomfortable and hot while wearing synthetic materials, these synthetics are known for their smooth feel and expert moisture-wicking abilities.
|Lightweight/comfortable||Holds odors (smelly)|
|Durable||Low breathability (depending on weave)|
Silk may not be the most mainstream material for base layers, but once silk fabric has been chemically treated, it’s also great at wicking moisture.
|Soft/comfortable||As an organic substance, it can mold and be damaged by mildew|
|Lightweight||Needs to be hand washed|
|Wicks moisture||Easily damaged by sunlight|
Have you ever heard the phrase, “cotton kills?” Well, there is some truth to that. But cotton itself doesn’t kill, being cold and wet is the true culprit. Cotton fabric is controversial in the outdoor space while some swear that it is the cause of all things bad, while others still persist on wearing jeans and not worrying about it.
In some situations, cotton should be avoided. Because cotton takes a longer time to dry than other materials and theoretically just retains the water, it’s recommended to avoid cotton for cold conditions. If it’s going to be cold and wet, then it’s doubly important to choose a fabric that will help you stay dry.
Cotton has a poor reputation in the camping and hiking world, but it’s not all bad. In fact, cotton base layers may be the best choice for a summer layer because they are more breathable and hold moisture (which actually cools you down). Cotton isn’t evil, it just serves a different purpose.
So unless you’re in a survival situation in the middle of a bitterly cold winter and have no clothing to change into if you get wet, odds are you’ll be just fine. I’m not going to tell you to wear or not wear cotton because it’s ultimately your choice.
However, it may be a good idea to avoid cotton in extreme cold conditions for safety purposes, but for sports or outdoor activities, it probably doesn’t matter. Just bring something to change into and you’ll be fine.
|Breathable||Can get very heavy when wet|
|Hypoallergenic||Some weaves are not durable|
Base Layer vs. Thermal: Is There A Difference?
The words ‘thermal’ and ‘base layer’ are often used interchangeably, but are they actually the same thing?
The answer is one that I don’t usually like to give: yes, they are the same… mostly. Base layers and thermals are pretty much the same things. Technically, thermals are a type of base layer that focuses on keeping you warm but not always as much on moisture-wicking.
The differences between the two almost remind me of that old math saying that we all learned in 6th grade:
All squares are rectangles but not all rectangles are squares.–Geometry
Squares always have four equal sides, but rectangles can have two different side lengths. In these terms, all thermals are base layers but not all base layers are thermals. Thermals are mostly designed to keep you warm, but some base layers may be designed for warmth AND to keep moisture off your body. So really, that’s a small difference.
If you want to learn more about the differences between base layers and thermals, check out my entire article here.
Should I Wear a Base Layer In the Summer?
This topic seems to be one that’s quite the controversy in the hiking world. To wear a base layer in the summer or not to wear a base layer in the summer?
While wearing a base layer helps to keep your body warm, it doesn’t do much to keep you cool in the hot temperatures of summer. If you’re really trying to go for the coolest option, you might as well forgo clothes altogether.
However, base layers are designed to wick moisture away from your body, so they can make you feel more comfortable in humid conditions. If you’ve ever been hiking in high humidity and have gotten so sweaty that you look and feel like you took a hot shower in 100-degree weather, then a lightweight base layer may start to sound appealing.
This truly depends on the individual. Some swear by a summer base layer while many just try and wear as little as possible. If you’re not comfortable, forget the science studies and do what works for you.
I will give one nod to a summer base layer in avoiding sun exposure. It’s not as glamourous as it sounds to get that farmer-tan skin from hiking in a t-shirt for hours and hours. It’s extremely important to be protected from the sun if you’re going to be out all day, and a base layer has way higher SPF than any lotion can provide.
Maybe not all hikers and outdoor enthusiasts opt to wear a base layer in the heat, but the right summer base layer can have some cooling effects. If you do choose to wear a base layer in the summer, go for one that’s lightweight (has thin material), is loose fitting, and moisture wicking.
To dive deeper into this subject and check out what 37 hikers have to say about wearing a base layer in the summer, check out the link to my article here.
Should I Wear Multiple Base Layers?
You know what they say? The more the merrier! Well, maybe there are a few exceptions to this rule and we aren’t entirely sure who ‘they’ is, but when it comes to base layers, you can absolutely double up. If the weather is cold and you need more layers to bundle up, adding a second base layer will add an extra layer of protection. Plus, the two layers can work together to keep moisture off your body.
Wearing two base layers at the same time will likely be tighter and insulate your body heat. Although, it could end up being too tight and make it harder for you to move around. The alternative is to use a base layer with thicker material because this should have a similar effect to wearing the two base layers.
If you want to learn more about wearing two base layers, check out my comprehensive article with this link.
Can You Wear A Base Layer On Its Own?
Even though you may have heard the term ‘long underwear,’ base layers aren’t really underwear. Base layers can be worn on their own, it just depends on the weather and how active you plan to be.
If you’re planning on camping in cooler temperatures, it might not be the best idea to rely on your base layer alone. As you now know, base layers aren’t meant to keep you warm; they’re meant to keep sweat and water off your body. So if you just use a base layer to stay warm during the winter, you’ll be cold.
If it’s 40 degrees and sunny and you plan to go winter hiking, cross country skiing, or snowshoeing, you might find that just a base layer is all you need. But, it might be a good idea to dress in layers anyway. When you’re moving around and getting your heart rate up, you’ll probably want to remove your middle and outer layers, which leaves just your base layer.
If you’re hiking in the spring or fall (50 to 60-degree weather), a base layer may be all you need. I’m more of a ‘prepare for everything’ kind of person, so I always bring some sort of weather-resistant outer layer in case it rains. But you’ll probably be comfortable in just your base layer.
A Guide To Making Base Layers Actually Work
Now that you know how base layers work and why they work, it’s time to learn how to choose the right base layer! To answer all the questions you may have about picking a base layer, read our comprehensive guide below.
How Tight/Loose Should My Thermals Be?
For your base layer to do its job to wick the sweat off your body and help you stay warm, the fabric has to be touching your skin. For cold-weather activities, your thermal should fit tight against your body and have no gaps that let air in. Your thermal shouldn’t be loose around your waist, wrists, or neck otherwise, the cold air could get through and your thermal won’t be able to do its job.
However, a loose-fitting thermal can be a good choice for warm weather camping and other outdoor activities. A loose-fitting thermal can still wick moisture from your body to keep you dry, but won’t make you feel too warm.
If you’re worried about whether your thermal will be too hot or cold (i.e., you’re not sure if your thermal is tight or loose enough), try doing a 20-minute weather test and wear your thermal outside. If you feel too hot or cold as you sit outdoors, then you aren’t wearing the right base layer. If you’re too hot, try wearing a looser-fitting thermal; if you’re too cold, go for a tighter fitting thermal.
Generally, if you’re confident you’ll be in 60-degree weather or warmer, you can get away with a loose-fitting thermal. But if the temperature could drop below 40 degrees Fahrenheit, wear a tighter fitting base layer.
Want to learn more about how tight or loose your base layer should be? I go into more detail on this subject in my article on this topic here.
What Thickness Of Base Layer To Choose?
The thicker the base layer, the warmer it will be. It makes sense if you think about it: thicker fabric makes more of a barrier between your skin and the air. So if you want a base layer that will keep you warm when it’s cold, choose a thicker thermal. However, you can achieve the same thing by layering your base layers, and many campers and hikers choose to do so.
Thinner fabric does a better job of wicking moisture away from your body, so anyone who plans on being active or doing winter training should go for a lighter-weight base layer. If you’re not sure if you’ll be warm enough with a light base layer, you can always double up and take layers off if you need to.
Base layers are often referred to as ‘weights’ instead of fabric thickness, so in the sections below you’ll see the common base layer weights and learn when to use them.
What Base Layer Weight Should I Choose?
The weight of your base layer depends on how active you plan to be and the weather you expect. The next few sections will outline when and why you would choose the common base layer weights.
Ultra-lightweight – Mild To Warm Temperatures
This weight of this base layer goes by many names, so you might also see ‘featherweight’ or ‘microweight.’ Ultralightweight base layers will have the thinnest materials, so they are best used for mild weather, such as a nice spring day that stays around 60 degrees Fahrenheit. While your base layer should be tight fitting most of the time, you might consider finding a looser-fit ultralightweight base layer for better breathability.
This style base layer can be used for:
- As a second base layer under a midweight or heavyweight.
- Hiking or camping in the late spring or early fall.
- Worn at night if the temperatures will be above 50 degrees Fahrenheit (any cooler and you might get cold).
Lightweight – Moderate to Mild Temperatures
Lightweight base layers are very similar to ultralightweight. The fabric is thin and the main purpose of a lightweight thermal is to wick moisture. So, it’s not the best choice for insulation. However, a lightweight base layer can be worn by itself if you’re doing some sort of outdoor activity or if the weather is moderate to mild.
Use a lightweight base layer for:
- A second base layer under a midweight or heavyweight.
- Hiking or camping in the late spring or early fall.
- When running, cross country skiing, snowboarding, or snowshoeing in mild winter weather.
Midweight – Moderate to Cool Temperatures
Midweight base layers can be the best of both worlds. When bundling up for an outdoor adventure, a midweight base layer may be a good choice as your first layer. It’s thicker than lightweight thermals, but not thick enough to make you uncomfortable in moderate (40 to 50 degrees Fahrenheit) weather.
It’s also the perfect base layer for a combination of activity and downtime, so you won’t get too cold if you’re taking a break from skiing or hiking. You could also use a midweight as a second base layer and take it off if you get too warm.
Wear a midweight base layer for:
- Outdoor activities such as camping, hiking, skiing, or snowboarding in moderate winter temperatures (25 to 40 degrees Fahrenheit).
- As the second base layer on top of a lightweight or ultralightweight thermal.
- If you’re that person who runs cold, use a midweight as the first layer under your everyday winter clothes.
Heavyweight – Cool to Cold Temperatures
Heavyweight base layers are the thickest of all weights of thermals, so they’re naturally the warmest. The purpose of a heavyweight base layer is to keep you warm by insulating your body, so it should be one of your layers if you plan to do some winter camping in below-freezing temperatures (around 30 degrees Fahrenheit).
Generally, heavyweight base layers aren’t worn as your first layer, so many outdoor enthusiasts will wear a mid to lightweight base layer underneath their heavy thermal. When you’re choosing a heavyweight thermal, you might notice that it fits looser than other base layers, which is exactly how it is supposed to fit!
Choose a heavyweight base layer if:
- You’re going winter camping and you plan on sitting.
- You need a second base layer.
- You’re going to be in the crowd watching winter sports (hockey, snowboarding, skiing, etc.). You’ll never be as cold as when you are watching an outdoor winter sport just sitting around.
I admit, I have a heavyweight thermal base layer and I’ve worn them even in 50-60 degree windy weather. They do get pretty warm in 60-degree weather but I don’t like being cold.
What Size Base Layer Should I Get?
When you’re thinking about buying a base layer, you’ll generally hear two completely different opinions. Some people say to buy your thermal a size smaller than normal because you want it tight, others may say to go a size up because they run small and are usually too tight. So, who’s right?
After reading about how your thermal should fit, you know that your base layer should be tight, but not tight enough to make it hard for you to breathe or move. This means that neither of the above opinions is correct, and you should stick to your normal shirt or pant size when buying a new base layer.
However, if you try on a base layer in your normal size and find that you can barely move and you can’t breathe normally, then you should try the next size up (or a different style or brand). On the other hand, if the thermal in your normal size feels too loose, then it won’t do its job to keep moisture out. If that’s the case, try a size smaller and see if that makes a difference.
What it really comes down to is the reason you’re buying a base layer in the first place. If you need a thermal for cold-weather camping, you’ll want a more fitted base layer. But if you want something light to wear on an easy spring hike, a looser fitted thermal will likely be more comfortable.
First try the size that you normally fit into and then adjust from there.
Do I Wear Clothes Underneath The Base Layer?
This is actually a really good question. If a “base” layer is meant to be the first layer, do you need clothing underneath it? Yes! While you can of course go commando, it’s perfectly acceptable to wear underwear under your base layer.
In fact, wearing something under your base layer will actually protect it because your sweat and smells will get on the clothes under your thermal instead of on your thermal.
Plus if you’re like me, you’ll be happy to know that you won’t have to wash your thermal as much if you wear something underneath it! Not only is it less laundry, but washing it fewer times will make your thermal last longer.
Check out our article about wearing underwear underneath thermals here.
Do I Wear ‘Normal Clothes’ Underneath The Base Layer?
Base layers and thermals are meant to be fitted, so it may be uncomfortable to wear a sweatshirt or t-shirt underneath your base layer. It could be especially uncomfortable if you don’t wear the right shirt because not all garments are designed to keep moisture out. Instead of having your thermal against your skin, a cotton shirt will hold that moisture against your body.
However, you can get away with wearing some light athletic shorts or spandex underneath your base layer if you want to protect your thermal.
Do I Wear Underwear Underneath The Base Layer?
I do have an entire article on this topic if you want more in-depth explanations on whether or not you can wear underwear under your thermal (use this link!), but to summarize:
Wearing underwear underneath your thermal won’t significantly change the function of the thermal. So it’s perfectly acceptable to wear underwear and it will likely keep your thermal cleaner longer. We’ve all heard that we should avoid cotton when outside in the cold, but wearing cotton underwear won’t be a death sentence.
Still, it might be a good idea to wear synthetic fabric for your underwear instead of cotton, just in case. And for the guys (or girls, if you choose to wear these), avoid wearing loose boxers and go for something snugger against the skin. You’ll be more comfortable and can avoid bunchy boxers in tight thermals.
What To Wear Over Thermals
As we discussed above, it’s perfectly acceptable to wear just your thermal and nothing over it. But if you’re going for the layers, there are plenty of options to choose from. You’ve likely seen this guideline in my other articles on base layers, but a general rule for layering is:
|Base Layer||Moisture-wicking; keeps you dry|
|Middle Layer||Insulation; keeps you warm|
|Outer Layer||Protection; keeps you safe from wind, snow, and rain|
You can find more in-depth explanations to what to wear over your thermal at this link of mine here, but in general, you can wear pretty much any of these over your base layer:
- Hiking pants (I have an awesome article on why you should wear these here)
- A second base layer
- Jackets (puffy or lightweight depending on the weather)
- Hat, scarves, gloves, and other accessories
Here’s an example getup that I wore during a run when it got to 9 degrees Fahrenheit, recently:
When To Wear a Base Layer?
Now that you know pretty everything about base layers, when should you wear them? And what activities should you wear base layers for? Find out below!
How Cold Does It Have To Be Before Wearing A Base Layer?
Much of this really depends on your body. If you run cold, then you’ll probably need a base layer before someone who identifies as a human furnace.
However, because base layers come in different weights you can get away with wearing a base layer at a wide range of temperatures. While a heavyweight base layer may not be appropriate for 60-degree weather, you can probably get away with wearing a lightweight base layer. It’s not the end of the world if you wear a too-thick base layer, you’ll just be uncomfortable. If you’re in scorching conditions than you might be in trouble.
Something else to keep in mind is your body’s ability to maintain your body temperature. Why do you ask? Because our blood vessels are more open or constricted depending on the time of the year, and that impacts your ability to tolerate temperatures.
The New York Times has a great article that explains this process. When we first experience cold weather, that first 50-degree day in the fall, perhaps, our blood vessels constrict (become tighter) and lets less blood come to your body’s surface. The blood is then driven to the center of your body and makes your skin feel cold. Thus, the 50-degree external temperature feels cold.
Still with me? Great! Here’s more:
But over the course of the winter, your body gets used to the cold temperatures and your blood vessels will dilate (get bigger) and allow the warm blood to come to the surface of your skin again. Then when spring comes around, you have warm blood at the surface of your skin, so the air feels warmer.
So if you’ve just gone from 85 degrees Fahrenheit to 50 degrees, then you might want a lightweight or midweight thermal. But if you’ve just come out of a deep freeze (20 degrees Fahrenheit or lower), you might be comfortable in a t-shirt in 50-degree weather.
Here are some temperatures associated with what you can wear to stay comfortable. Your personal mileage may vary
|Temperature||What to Wear|
|50 to 60 degrees||Shorts with a lightweight shirt, jacket, or thermal. can work well, here. If it’s windy, a windbreaker can make a huge difference in staying comfortable.|
|40 to 50 degrees||For bottoms, a light to mid baselayer with any thick layer of clothing like sweat pants will work well. For a top, a long-sleeve shirt with a sweatshirt or a windbreaker.|
|30 to 40 degrees||Time to get serious. For bottoms, you should have a mid to heavy-weight base layer, an insulating layer (like sweat pants), and a windbreaking outer layer to keep out the cold wind. If your windbreaking outer layer has a fleece liner you might be able to skip the insulating layer. For tops, a mid to heavy-weight base layer with an insulating layer (like a fleece), followed by an impervious outer layer such as a rain jacket or a snow jacket. A hat and gloves are good ideas at this temperature.|
|20 to 30 degrees||This is reasonably close to the 30-40 degree category with a few changes. Gloves and hats are now non-optional. If your jacket doesn’t have a hood then ear warmers are incredibly helpful. You might want to switch out your rain jacket for a snow jacket with more insulation.|
|10 to 20 degrees||Heavy-weight thermals top and bottom, insulating layers top and bottom, and outer-shells that will keep out wind and water. Additionally, make sure to have your neck and face covered. You will appreciate wearing thick wool socks–even two pairs is not a bad idea.|
Another thing to keep in mind is that this temperature guide is for outdoor activity. If you’re going out but plan to have downtime or plan on doing a lot of sitting, use the suggestions from the next colder set of temperatures.
What Activities Do I Need To Wear A Base Layer?
While base layers can be used for pretty much anything (even under your everyday clothes), there are certain activities that you should be mindful of what base layers you wear. Check them out below!
For running, you should wear base layers for both your top and bottom. You want to make sure your base layer is good at wicking moisture so that you stay dry, but you also want to stay warm. So, choose a lightweight base layer and put a jacket over it.
When it comes to base layers for climbing, upper body mobility is important. That being said, try for a looser fitting base layer that won’t restrict your arm or chest movement. Not only will you be more comfortable, but you’ll avoid chafing.
For camping, your base layer will depend on the temperature and how active you plan on being. If the weather is moderate (60-70 degrees F), you should be fine with a midweight or lightweight thermal. But if you expect cold temperatures, choose a heavyweight thermal. If you aren’t sure, it wouldn’t hurt to double up your thermals just to be safe.
In general, you’re not working up a big sweat when camping so planning for the warmest clothing is not a bad option.
When you’re hiking, you want to be comfortable. So, choose base layers that offer good mobility and that wick moisture so that you stay dry. Similar to camping, the thermal you choose will depend on the weather. As always, feel free to double up.
When you’re snowboarding or skiing, it’s a good idea to wear some base layers. Because you’ll be out in the snow, you should go for at least a midweight, but you could also a layer with a lightweight thermal underneath so you can take off layers if you get warm.
I’ve been amazingly warm while snowboarding because your body is working tremendously hard. It’s very important to have an insulating layer ready when you’re on the lifts or when you take a break and the cold comes.
Kayaking and Canoeing
Same as climbing, you’ll want a looser base layer that doesn’t constrict your arm movements.
5 Tips For Base Layer Care
Taking care of your base layer is every bit as important as choosing the right one. This PDF was adapted from articles on REI’s website and is a great resource for thermal care. I took the best tips and summarized them below.
By wearing clothes or underwear under your base layer, you protect it from smells and sweat. That way, you can avoid washing your thermal after each use and it will last longer.
Look At The Label
The label is the best place to look for washing instructions. By looking at the label (or looking at the website/company that make the base layer) you’ll know exactly how to wash it and what to avoid.
All fabrics are subject to shrinkage, albeit some more than others. By air drying, you can avoid shrinking fabric altogether.
Use Specialized Technical Fabric Cleaners
To avoid reducing your base layer’s performance, use specialty cleaners that are designed to maintain your base layer’s wicking ability. Such as:
Avoid Fabric Softener and Dryer Sheets
Oddly enough, the oils, scents, and waxes used in fabric softeners and dryer sheets reduce clothing’s ability to repel water, breathe, and wick moisture. So, stay away from these products when washing your base layers.