Hair colouring: what a dermatologist should know?

<p>Hair is an important part of body and a major factor in self-image. A wide variety of hair cosmetic preparations are available and are used regularly by most of the world’s population. Hair colouring is one of the commonly done procedure. However, any chemical treatment, normal grooming habits and environmental exposure can produce changes in hair texture or hair breakage. It is necessary for a dermatologist to know the basis of hair colouring, the procedure and the possible side effects it can cause. Also post colour care is also to be known about to prevent further damage to treated hair. This article explains the basic chemistry and mechanism involved in hair dyeing and the basic facts a dermatologist should know.</p>

Secreted Frizzled-related protein 4 inhibits the regeneration of hair follicles

Secreted Frizzled-related Protein 4 (sFRP4) belongs to Wnt inhibitors. Previously, we reported that sFRP4 inhibited the differentiation of melanocyte. Here, by using of immunostaining, we showed that sFRP4 is expressed in both human and mouse hair follicles, especially in the outer root sheath and inner root sheath. To reveal the role of sFRP4 in hair follicle growth and hair cycle, we induced synchronized hair cycle in the dorsal skin of mice by depilation, and injected sFRP4 intradermally into the skin. By hematoxylin and eosin staining, we found that the regeneration of hair follicles was inhibited by sFRP4. However, the structure of hair follicles remained complete. Compared with phosphate buffer saline-treated hair follicles, the sFRP4-treated hair follicles still had the same expression pattern of keratins. Our findings reveal that sFRP4 inhibits but not blocks the regeneration of hair follicles, and supply a potential therapeutic application to treat hair follicle regeneration disorders.

Simultaneous RP-HPLC-DAD determination of dansyl amino acids in chemically treated human hair

A simple, rapid and reliable RP-HPLC-DAD method for the analysis of 19 amino acids in the protein hydrolysate of chemically treated hair is developed. The pre-column dansylation and RP-HPLC separation were optimized and peak resolution was improved as compared to previously published HPLC methods. The developed method showed excellent linearity for all tested amino acids in the concentration range 0.05-0.5 mmol/l. The obtained results show that the concentration of all amino acids detected in bleached hair decreases with increasing the concentration of hydrogen peroxide, this is most significant for cystine, compared to virgin hair. Higher amounts of the typical amino acids for keratin have been measured after exposure of hair to protein treatments. The method has been shown as very useful for amino acids analysis in a protein hydrolisate and it can be also used for establishing the amino acid profiles of other protein samples using this optimized procedure.