Dry skin is dependent on various external and internal factors.

Internal factors include:

• Biological skin ageing (as we age, there is reduced cell turnover, and diminished secretion of sweat and production of sebum)
• Hormonal influences
• Certain illnesses or other skin conditions
• Genetic factors.

External factors include:

• Environmental factors, including dry air from central heating systems and air conditioning
• Contact with chemicals, including washing detergents and soap (e.g. contact dermatitis)
• Certain skincare products and medical preparations
• Poor diet
• Smoking
• Exposure to UV rays. All of these factors can reduce the skin's moisture content, resulting in dry, rough and possibly cracked skin.