Causes of dry skin

Most dry skin is caused by environmental exposures, such as:

* Weather. In general, your skin is driest in winter, when temperatures and humidity levels plummet. Winter conditions also tend to make many existing skin conditions worse. But the reverse may be true if you live in desert regions, where summer temperatures can top 110 F and humidity levels sink to 10 percent or less.
* Central heating and air conditioning. Central air and heating, wood-burning stoves, space heaters and fireplaces all reduce humidity and dry your skin.
* Hot baths and showers. Frequent showering or bathing, especially if you like the water hot and your baths long, breaks down the lipid barriers in your skin. So does frequent swimming, particularly in heavily chlorinated pools.
* Harsh soaps and detergents. Many popular soaps and detergents strip lipids and water from your skin. Deodorant and antibacterial soaps are usually the most damaging, as are many shampoos, which dry out your scalp.

Other factors
Other factors, including certain diseases, can significantly alter the function and appearance of your skin. These include:

* Psoriasis. This skin condition is marked by a rapid buildup of rough, dry, dead skin cells that form thick scales.
* Thyroid disorders. Hypothyroidism, a condition that occurs when your thyroid produces too little thyroid hormones, reduces the activity of your sweat and oil glands, leading to rough, dry skin.
* Alcohol and drugs. Alcohol and caffeine can visibly dry your skin. Prescription drugs such as diuretics, antihistamines and isotretinoin (Accutane) also have a drying effect.
* Dehydration. Severe diarrhea and vomiting, a high fever, profuse sweating during exercise or simply not drinking enough liquids can cause your body to lose more fluid than you take in. One of the first signs of dehydration is skin that has lost its elasticity.