First of all, what do base layers really do for you?  Generally speaking, they act as a “second skin,” helping to keep your actual skin dry and at a comfortable temperature throughout your activities.

With several different types of base layers on the market, which should you choose?  Synthetic, merino, and blended fabrics are a few examples of the options available. Synthetic base layers are also sometimes offered in a compression format.

For simplicity’s sake, today we will focus on two of the major materials in the outdoor industry: synthetic versus merino.  Both fabrics have their ups and downs, so it’s important to know the differences to get the specific performance that you desire.

Broadly speaking, synthetic base layers are made out of materials like nylon, polypropylene, polyester, rayon, and spandex.

base layerThe North Face Base Layer


✔ More durable than merino.

✔ Quicker drying than merino.

✔ Inexpensive compared to merino.

✔ Very light.

✔ Only absorbs 1% of its weight in water.


✖ They hold odor.

✖ Petro-chemical based.

✖ Prone to heat damage.

✖ Generates static electricity easily.

✖ Non-biodegradable compared to natural fibers.

synthetic fiber

Synthetic Fiber Zoomed to 18um 

Merino wool is a natural fiber from the merino sheep of New Zealand. Unlike traditional wool, merino fibers are smoother and are not associated with the itchiness of regular wool. Merino sheep live in extreme climates that range from very hot to very cold, so their coats have developed the qualities necessary to be comfortable in many climates. This makes the merino fiber ideal for base layer material.


✔ Does not hold odor.

✔ Naturally flame retardant.

✔ Static electricity resistant.

✔ Naturally wrinkle resistant.

✔ Natural UV protection.

✔ Biodegradable and renewable.


✖ Heavier than synthetic fibers.

✖ Takes longer to dry than synthetic.

✖ More expensive than synthetics.

✖ Not as durable as most synthetics.

✖ Absorbs 20% of its weight in water.

merino wool fiber

Single Merino Wool Fiber 

Both merino and synthetics work for all seasons and conditions, but the properties noted above influence the “ideal” scenario for the fabrics.  It is also important to note that although synthetics can be lighter and more durable than merino, that is not true in every case. Garment construction influences the basic list above heavily. Merino fiber has many naturally occurring benefits to base layers, whereas synthetics are often modified with chemicals to improve their performance.

A well made synthetic base layer is good for a “fast and light” type of person on a budget who is aiming for high performance.

A well made merino base layer is ideal for an environmentally-conscious person with a higher budget who is interested in the features naturally present in the material.

Both merino and synthetic base layers are fantastic.  Ultimately what it comes down to when making a decision is personal preference.  Many people will own a combination of the two materials with different uses in mind. For example, for long winter expeditions someone may choose merino for its non-stinking quality.  For a day-long summer mountain bike race in a humid climate, an ultra-light synthetic may be someone’s first pick.  With the many different weights and styles of base layers available, you can choose based on your specific preferences.>

Use the basic knowledge presented here as a base for your own research, and then start experimenting!  It may take you a while to find your perfect garment for each activity, but rest assured, merino and synthetic will both take care of your basic base layer needs in any case.  Remember, the goal is to get outside.  Having the proper gear will get you prepared so that you can stay outside, and stay comfortable.

ॐ Orion Miller