Conventional hair permanent waving (PW) and permanent straightening processes typically involve two steps: reduction, for breaking ‐S‐S‐ bond in cystine into cysteine and oxidation for ‐S‐S‐ bond reconnection. However, it is known that the hair incurs damage during the oxidation step. In this work, we proposed a novel strategy to reconnect reduced disulfide bonds in hair via the thiol‐Michael click reaction, by using a symmetric Michael reagent.

With the rapid growth of beauty and personal care industries, many hair-relevant products, hair dyes and hair perms in particular, are increasingly prevalent in both women and men, regardless of being young or old as they frequently change hair color or shape to enhance youthfulness and beauty and to follow fashion trends. Hair dyes and perms alter hair color and/or shape by mechanically changing the physical structure and chemical substances of the hair shaft. However, treatment of hair with chemical formulations has been potentially ascribed to adverse outcomes in the hair shaft including structure damage, chemical constituent disorder, and impaired physical properties, although hair cosmetics procedures are intrinsically safe. Nevertheless, the mechanisms of impairment in the hair shaft and scalp induced by hair dyeing and perming remain elusive. Additionally, adverse reactions activated by exposure to specific chemical ingredients including skin irritation, allergic contact dermatitis (ACD), and even cancer risk have been reported clinically, but existing evidence is not consistent enough in the case of human studies. Herein, the review aims to give an overview of hair cosmetics, especially concerning the basic knowledge about various hair dyes and perms, the consequences for hair shafts and the scalp resulting from the application of hair cosmetics mentioned above, mechanisms of hazardous outcomes, and potential desirable interventions to alleviate the impairment.

Hair represents an important aspect of human individuality. The possibility of having an easy to handle hairstyle and changing it from time to time promoted an increasing search for chemical hair transformations, including permanent wavings (PW). PW is the chemical process used to convert straight into curly hair. Significant findings have been made in this field within the last three decades. In the past few years, PW has come back up to date, helping to define curls in wavy and curly hair and to create waves in straight hair. "Afro permanent" and "Beach waves" are some popular names for these new uses of PW. The primary safety concerns for PW generally arise from misuse or failure to comply with the product's usage instructions. Skin irritation, hair breakage, oral toxicity, sensitization, and scarring alopecia have been reported in the literature. Therefore, dermatologists need to understand well this matter to properly advise patients on how to get the best outcome without hazards. This review aims to discuss the main types of reducing agents used, the different techniques, the consequences to hair shafts, and the most important patients' recommendations on this topic.

chemical breaks open the disulfide linkages between the polypeptide bonds in the keratin; the protein structure in the hair. The disulfide bonds give hair its A permanent wave, commonly called a perm or permanent (sometimes called a "curly perm" to distinguish it from a "straight perm"), is a hairstyle consisting of waves or curls set into the hair. The curls may last a number of months, hence the name. Perms may be applied using thermal or chemical means. In the latter method, chemicals are applied to the hair, which is then wrapped around forms to pro A… By 1930, the process of permanent-waving was well established and its importance can be gauged if one considers that the majority of middle-class women, at a rough estimate, had their hair set once a week and permed perhaps once every three months as new hair replaced the waved hair. Meanwhile, hairdressers sought to improve the process and reduce the work involved; this meant savings at the lower end of the market and yet more women getting their hair permed. This was also stimulated by pictures of the rich and famous, particularly film stars, who all had their hair permed. This resulted in many copies of the original equipment being made by… Nestlé… In 1938, Arnold F. Willatt invented the cold wave, the precursor to the modern perm. It used no machines and no heat. The hair was wrapped on rods and a reduction lotion containing ammonium thioglycolate was applied. This chemical breaks open the disulfide linkages between the polypeptide bonds in the keratin; the protein structure in the hair. The disulfide bonds give hair its elasticity, and can be reformed with chemicals. Next, an oxidation lotion—hydrogen peroxide—was applied to close the disulfide bridges again, and the hair was reformed to the shape of the rod. The entire process took 6–8 hours at room temperature. In the 1970s, acid perms were invented. These ammonia-free acid perms, sometimes called buffered waves, use glyceryl monothioglycolate in the place of ammonia. Acid perms, or buffered wavers, are slower but gentler to the hair. Heat is usually added by placing the client under a dryer, after covering the wrapped head with a plastic cap. The reaction is endothermic and the additional heat causes the pH to rise from 6.9 to 7.2. Perms today use this method with sodium thioglycolate instead of ammonium thioglycolate, at a pH of 8 to 9.5. Perming hair with the sodium thioglycolate method takes only 15–30 minutes of exposure to the sodium thioglycolate solution before a neutralizer solution is applied to bring the pH back to normal and re-bond the hair. The permanent relaxer straightens the hair instead of curling it. The same chemical methods can be used for this, but the hair is not wrapped around rods.

Hair is the ultimate personal beauty tool of self-expression. It is more malleable than skin and it is more personal than clothing; however, hair does not remain constant with age. Hair is arguably in peak condition at about 30 years of age. With time, there is a gradual change in many aspects of hair: hair diameter is reduced, hair density is decreased, androgenic alopecia may develop, and pigmentation may be diminished, producing a significant psychological impact. These age-related changes can be exacerbated by blast drying, heat straightening, perming, and coloring. In this review, the changes in hair fiber and array (collection of fiber) properties that occur during aging and the impact on styling and potential interventions that consumers undergo to circumvent these issues are discussed.