Health index is the first and the most important factor when it comes about the warm underwear . Warm underwear is much different from other winter clothing, it is to wear so close-fitting .The comfort level requirements are much higher. How to choose warm underwear both keeping warm and healthy . Touch it with your hands .High quality underwear requires higher among middle insulation layer when they are relevant manufacturing, using superfine fibers (diameter less than 1.2). The Intermediate comb, composite technique are also relatively advanced, the garment surface and the oneness are strong, the dress function is also better. Therefore,if you touch it by hand , feeling soft and without impurit products shows that its material is good. You can see the fabrics . As the standard , the product packaging should mark that the warmth retention warm underwear and the unit grams warmth retention .And, the warmth retention property shall not be lower than 30% .The warm underwear may also marke formaldehyde content or other environmental protection index. But this is not compulsory, many brands do not have this one. The warm underwear on the market can be divided into three gears from high to low as the quantity . The more containing cotton in the surface fabric, the higher the quantity is, and its softness and porosity are also better . The underwear using colored cotton as raw material , matching with a little stretch leica, belong to high-quality gens of the cotton underwear goods. One more is the PH .As for the clothes ,especially ones directly contact with the body, the more attention to health is concerned .According to the state regulations, factors of clothing, ones having direct contact with the skin the PH value should be controlled in 4.0 to 7.5,for others, PH value should be controlled between 4.0 and 9.0. But many brands on the market simply labeled "category B", and having no detailed content, so you should buy this kind of clothes carefully. Ones with PH value too low or too high will be harmful to human body, especially children, you had better choose certain brand of some prestige. Another is good elasticity . Because the close-fitting clothing has certain force so that in the cover of the coat, we won't appear too overstaffed. Both cultivating one's morality, and keeping warm, this also is test for the warm underwear. Having judged such factors,you can find a heathy one easier.