Hair relaxers have expiration dates. Hair relaxers are formulated with a chemical called sodium hydroxide, which has a shelf life of one to 1.5 years.
When a hair relaxer is used past the recommended shelf life, the consumer can get unfavorable results because the original formula becomes compromised. It may not perform as effectively as it initially would, and the formula may be unstable, impairing the actual application to the hair. Uneven results may also occur in the consumer's hair, because once the relaxer separates, some parts of the product may be more potent than others. Finally, a consumer may be harmed by the use of an expired relaxer if bacterial growth occurs in the product. If a relaxer containing harmful bacteria is applied to the skin or inadvertently in an eye, severe reactions or infections can occur.