Layers that are closest to the skin (like underwear) are the most important. Body exudes toxins and also absorbs them back if there is not enough ventilation - like in clothes made of nylon. That is why so many people react negatively to "plastic" underwear. Moisture and toxins trapped without clothes "breathing" can create damage. Try organic and natural underlayers for healthier options. Natural textiles worked for people for thousands of years.
Natural and Organic