Like all sheep, merino breeds of sheep grow a new fleece every year and they have to be shorn to be comfortable. Unlike synthetic fabrics, many of which are made from plastics, wool does not require anything to be mined or processed. Sheep can often graze on land that is too marginal for growing crops or even, in some cases, raising other animals. The variety of merino types means that there is one that can handle almost any climate. Oh, and they don't use the pesticides required in cotton production, either.

Because it is so much finer than traditional wool fabrics, it is one of the softest fabrics available (perhaps falling short only of cashmere) and not itchy when worn next to the skin. This makes merino perfect for a bottom layer in cold weather, trapping air against your skin without compromising comfort. In fact, merino shirts can be finer than cotton shirts, making it hard to even believe they are actually wool. Many people with wool allergies also find that merino wool is hypoallergenic, although testing it before you go on a long trip is still a good idea. Because merino base layers and midweight t-shirts are so comfortable, they are actually ideal for sleeping in if you are camping in cold weather or at altitude.

Another reason to wear merino next to your skin is that it wicks moisture and sweat away, keeping you dry and comfortable. This means that even though you're wearing wool clothing, you aren't going to overheat. It also reduces odor while trapping warm air next to your skin on colder days. Be aware that because merino absorbs so much water it can take longer than some other natural fibers to dry.

Normal wool tends to be heavy. Merino is much lighter for the same amount of warmth. This means that your merino sweater will fit much more easily into a backpack or your luggage. Merino is thus perfect for deep wilderness trips where you have to carry everything or stock trips where you have a dunnage limit. It is also thin, meaning you don't have to buy boots that are a size too big in order to fit your wool socks under them.

So, if you get caught out in the rain, no big deal. If you are wearing merino wool garments, you can keep going right through that stream without having to stop and change, all without fear of losing heat from this natural insulator. It also does not gain as much weight from water as coarser wool products.

Synthetics tend to create an atmosphere where odor causing bacteria thrive, creating that odor which makes your hiking partner walk five feet ahead of you. Wool, on the other hand, contains lanolin, which has antimicrobial properties that once protected the sheep from skin conditions. Making a merino shirt stink takes talent and effort. You can wear it for multiple days. This is another thing which makes merino a particularly good material for hiking socks and hiking clothing.

Merino wool has a higher level of UPF than cotton, without being too heavy, which makes it perfect for natural sun protection. Between this and the fact that it wicks, you can wear it as a "sun shirt," especially at high altitude. It will protect you from sunburn and windburn without causing you to overheat.

Merino wool has elastic properties so it won't interfere with your activities, particularly if you are, say, climbing or snowshoeing. This is another reason why it is a great bottom layer, as you can wear skin tight merino as a base layer without worrying about whether it will work with your body. And as a nice side effect of this, it tends not to wrinkle either, meaning if you throw it into a backpack or a saddle bag without really paying attention, it will be fine. Some merino items, such as socks, will actually bend and mold to the shape of your body with time, and become even more comfortable.

Wool in general is more breathable than synthetics. Thin merino fibers have enough breathability to let air out of them and keep you from overheating, but when it gets cold you can still put a heavier layer on top to trap the air and heat. This makes merino very flexible. You can wear it on its own on warm days or as a base layer on cold days. It even reacts, at some level, to the temperature and helps you stay cool on warm days. It is very hard to overheat while wearing merino.

Because it's basically just hair (keratin), it decomposes in a matter of a few years. This also means it causes fewer problems for wildlife than synthetics if you literally lose your shirt. Rather than being toxic, it will end up being torn apart and used by birds for next liner or by other critters to make a bed.

You know how wool tends to pick up a charge and give you a bit of a prickly shock? Merino wool won't do that. And it also won't pick up dirt and dust as much as other wool items, meaning that when you wear it for three days in the back country you will still be able to tell what color it started out as.

It's that lanolin again. The lanolin tends to protect the surface of the wool and helps keep things like coffee, soda or, heaven forbid, blood from staining. And we've all got blood on our hiking gear, come on, admit it. This also means that, again, you can spend a couple of days in merino gear and still come into town and not feel like the Alaskan mountain man making his six monthly trip to civilization to get fuel. Anything which reduces the weight you have to carry is good.

Well, provided you're careful. You do need to wash it cold (delicate cycle on machines that don't allow you to set a temperature), or it may shrink. You can use regular detergent, but wool detergent will help your merino clothing last extra long. You can even tumble dry it on low heat if you need to, although it should be flat dried when possible as tumble drying will slightly shorten its life. (However, never use bleach or fabric softener on merino items. Softener will leave a residue that interferes with the fabric's ability to wick). Some merino items may be hand wash only, so do check the label. Always wash items inside out, especially if they have print. Check the label, but note that merino is reasonably easy to care for, especially when compared to other wools.