Permanent Waves are treatment of the hair intended to produce curls or to alter existing curls. In cosmetology, it is termed a type of curl reformation. Humans have been attempting to add curl to straight hair for thousands of years. The ancient Egyptians did this by wrapping their hair around wooden sticks; slathering it with mud from hot springs; letting it bake dry in the sun and then removing the mud. Presumably the mud had an alkaline chemical makeup that helped to set the curls. The safety of Permanent Waves is established by selection of ingredients that are safe and suitable for this purpose. In addition, Permanent Waves are rigorously assessed for their potential to cause scalp and eye irritation. Product safety is also established though strict adherence to the principles of Quality Assurance and Good Manufacturing Practices. This includes testing the compatibility of the product with packaging as well as shelf-life stability. It is especially important to follow the directions on the label of the product to ensure that the product performs as intended and that there is no irritation to the skin. Finally, the safety of products is monitored in the market-place through reports of consumer comments and complaints. Companies include a phone number on their products where comments or complaints may be reported.