Wool, common name applied to the soft, curly fibres obtained chiefly from the fleece of domesticated sheep, and used extensively in textile manufacturing. Wool may be differentiated from hair mainly by the nature of the scales that cover the outer surface of each fibre. Because of its crimp, or curl, wool has considerable resilience. This quality, together with its high tensile strength and elasticity, gives fine woollen fabrics the ability to retain shape better than cloth made from other natural fibres. Other characteristics of wool, which make it especially desirable for wool bedding, wool blankets and wool comforters, are its lightness, its ability to absorb moisture, and its insulating properties. It used to be in the past, that wool bedding was associated with such words as "heavy", "scratchy" and "itchy". Nowdays it is extremely soft, cozy and warm. It does not impede the whole body's perspiration and keeps it evenly warm. It is very attractive either. The cotton casing is woven very tightly and is smooth. Very often manufacturers offer three types of wool comforters: Summer (for tropical areas), Spring/Fall (of medium weight) and Winter (for severely cold regions and for those people who prefer to sleep on the covered porch. Almost all of organic wool bedding does not contain toxic substances, depleting the ozone layer and dangerous for inhaling. Careful quilting prevents wool fill from shifting and bunching. Pure wool is able to regulate body temperature, thus making a consumer always comfortable. Bedding edges are often serged. The wool fill is usually quilted to the casing. Summer type wool bedding is ideal for sleeping in summer, for those living in the tropics, for those whose house is usually kept warm during the whole winter and for those who don't need a lot of help to keep warm. The wool filling does not migrate to the corners of wool blankets and does not create cold spots because the fill is quilted to the cotton cover. Spring/Fall bedding is very comfortable when nights get colder in autumn and in spring and when the temperature changes quickly. Winter type wool bedding contains heavy weight wool comforters which demonstrates the highest degree of warmth keeping. It is made for people living in the north and for those who prefer to sleep under a cozy, warm comforter all year round. They can also serve as a substitute for down comforters. Most of wool comforters, mind you, are not machine-washable. Normally it is recommended to encase your wool comforter into machine-washable cover in order to protect it. It is also advised to air the comforter for some hours, under the sun, in order to keep it always fresh. You may do it every month. It is necessary to keep your comforter away from excessive sun exposure and from humidity. Quality of sleep, as researches determined, depends considerably on one's bedroom and on a bed in particular. An uncomfortable bed may be the reason of poor sleep a night. That's why if you experience sleepless nights, suffer from back aches, you are allergic or sensitive to different chemicals, pay attention to your bed and wool bedding. Bedding, containing such chemicals as arsenic and formaldehyde, may produce vapors causing a lot of health problems, like sore backs, asthma and numerous chemical sensitivities.