Hair Perms, Straighteners, and Styling Agents

The document from 2013 describes the structure of the hair shaft and the chemical processes involved in hair styling, such as temporary and permanent waving, straightening, and the use of styling agents. Temporary waves are created by breaking and reconnecting hydrogen bonds, while permanent waves alter disulfide bonds using an alkaline reducing agent and an oxidizing agent. Negroid hair requires an additional straightening step before waving. Hair straightening can be done mechanically or chemically, with chemical relaxers using strongly alkaline agents in a heavy cream formulation. Styling agents, including gels, mousses, and sprays, have evolved to include microemulsions and synthetic polymers for improved aesthetics. The document also notes that fragrances are the most common allergen in hair styling products, which often include sunblock ingredients and emollients due to their leave-on nature. It concludes that using hair perms or treatments up to 3 to 4 times during pregnancy appears to be safe.