Concealers are products that are intended to conceal or cover up skin imperfections on the face. They typically work by applying color to the skin or through other effects such as the reflection of light or the shininess of the skin. They can be applied using a brush, cloth or spray and are typically used in conjunction with Foundations. Concealers contain ingredients that apply color where it is needed in a precise and controlled manner. Concealers safety is established by selection of ingredients that are safe and suitable for this purpose. In addition, Concealers are assessed for their potential to cause skin irritation or cause allergic reactions. Product safety is also ensured 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. Finally, the safety of products is monitored in the market-place to track any consumer comments or complaints. Companies include a phone number on their products where comments or complaints may be reported.