What is often added to a protein treatment to increase its penetration into the hair shaft?

In the context of hair treatments, heat is effective in expanding the hair cuticle, allowing for deeper penetration of protein treatments into the hair shaft. When heat is applied, it opens up the cuticular layers, creating gaps that enable the protein molecules to more easily enter and fortify the inner structures of the hair. This process can significantly enhance the efficacy of the treatment, as the penetration of proteins is crucial for repairing and strengthening damaged hair.

Other factors such as cold air and water have different roles in hair care, but they do not assist in enhancing the penetration of protein treatments as effectively as heat does. Cold air can help seal the cuticle after a treatment but does not encourage the absorption of proteins. Water may assist in hydrating the hair but doesn’t increase the penetration of proteins during a treatment application. Oil is often used for moisturizing or sealing in moisture but does not facilitate the delivery of protein into the hair shaft. Therefore, heat is the most beneficial factor in promoting the penetration of protein treatments.