Some smoothing products contain formaldehyde or glutaraldehyde (see specific info), especially the keratin smoothing or Brazilian Hair Straightening. Formaldehyde and glutaraldehyde have mutagenic properties and are potentially carcinogenic. Its use has been limited in many countries. Other straightening products, such as sodium hydroxide, lithium hydroxide, calcium hydroxide or ammonium thioglycolate, used in the so-called Japanese Straightening, are not mutagenic and hence considered safe. It is recommended to limit its use, avoid products containing formaldehyde, meet the safety standards for use that appear in containers, keep clean the chest area and wear short hair or tied hair to prevent the absorption of potentially toxic compounds by the infant. Hairdressing's workers are more exposed and must strictly enforce safety rules (gloves wearing and time limitation, etc.) along with the use of legally approved products. See below the information of these related products: