Headwear is a very useful item of clothing that helps protect the head and face from the cold, rain and is also for UV protection against prolonged exposure to the sun. Many mid layer and outer layer jackets already provide a hood for protection and sometimes that is adequate enough. All headwear generally needs to be comfortable and lightweight, whether it be hats, glasses or scarves as they generally stay worn throughout the outdoor activity.
Hats and caps are essentially designed to cover the top of the head and provide insulation for heat and to provide waterproofing where relevant. There are a diverse range of products available with a variety of features. In the end, the main properties worth making sure of is that the hat is comfortable and lightweight as previously specified. Caps are a very simple form of UV protection for light hiking whilst winter hats can provide heat insulation and ear flaps to keep the head warm at little expense.
Glasses are mainly known for providing UV protection, but can also provide protection against wind, rain and loose material that may be flying with the wind (snow, dirt, mud). Generally a good pair of sunglasses with polarisation and/or basic UV protection is good enough for most activities, however transition lenses, foam gaskets and head bands can further enhance the use of glasses to help when conditions get extreme. Other bespoke properties such as impact resistance or ballistic ratings can also be a necessity dependent on the activities.
The one time where cotton could potentially be of very good use is with face scarves. The primary use of a scarf is to insulate the face from the loss of heat and to protect the mouth from foreign agents. Generally speaking, cotton is not advised where it could get wet, however it is debatable as it retains heat very well and is very comfortable to the skin. This does not mean that synthetics are not superior, however it’s worth elaborating that normally cotton is not recommended due to the retention of water when a person sweats. As scarves as tertiary, they are normally focused for comfort and insulation.