Hair and amino acids: the interactions and the effects

The interaction and the function of some amino acids in hair care applications are discussed. When amino acids are applied to hair in the form of simple aqueous solution, uptake of the amino acids is mainly controlled by ionic equilibrium. When amino acids were incorporated in a hair conditioner, the result was quite different, suggesting the importance of interaction between the amino acids and the cationic surfactants. Uptake of pyrrolidone carboxylic acid (PCA), a derivative of glutamic acid, is enhanced by combining with arginine, an amino with strong affinity towards hair. Effects of some amino acids on bleached/dyed hair are described. A hair conditioner incorporated with alanine improves hair surface hydrophobicity of bleach-damaged hair. Histidine and phenylalanine improve tensile strength. PCA was proved to be effective to improve color-retention of dyed hair.

Percutaneous penetration of hair dyes

Scalp penetration of 7 hair dyes (oxidative and direct) that occurs under conditions of hair dye usage was evaluated for both rhesus monkey and man using 14C labeled materials by quantifying their absorbtion via urine assays. Both species showed a remarkably similar pattern of dye penetration. The extent of scalp penetration is slightly higher for direct dyes but in neither case does it exceed 1% of the applied dose.

Percutaneous absorption of hair dyes: correlation with partition coefficients

A homologous series of hair dyes was selected for percutaneous absorption studies with excised human skin. The permeability constants obtained for the dyes were compared with octanol/water and skin membrane/water partition coefficients. The compounds examined were: p-phenylenediamine, o-phenylenediamine, 2-nitro-p-phenylenediamine, 2-amino-4-nitrophenol, 4-chloro-m-phenylenediamine, and 4-amino-2-nitrophenol. Skin absorption of the dyes was observed when they were applied in an aqueous solution. With one exception, the octanol/water partition coefficients were in the same rank order as the permeability constants. The determination of the partitioning of the hair dyes between water and either stratum corneum or epidermis was more complex. Preliminary stratum corneum/water partition studies resulted in values that were in the reverse order of skin permeation. When binding of the compounds to components of the membrane was saturated, the partition values more closely duplicated the rank order of permeability of the dyes. Prediction of percutaneous absorption of substances based on their partition coefficients may be confounded if these compounds are capable of binding to skin.

Skin penetration by 2,4-diaminoanisole in the rat

The absorption of 14C-labelled 2,4-diaminoanisole together with its reaction products was investigated after application to the skin of rats. 2,4-Diamino[14C]anisole was applied as an ingredient of three different hair-dyeing formulations using procedures approximating to realistic conditions of use. Percutaneous absorption of the compound ranged from 0.26 to 1.1% of the administered dose, according to the formulation used. Elimination occurred mainly in the urine, with a smaller proportion in the faeces. Very small amounts were detected in the expired air. Complementary investigations involving subcutaneous or oral application of a solution of 2,4-diamino[14C]anisole.2HCl showed that radioactivity was rapidly eliminated in the urine and faeces. Biliary excretion was demonstrated after oral administration.

Percutaneous absorption of 2-amino-4-nitrophenol in the rat

The absorption of 14C-labelled 2-amino-4-nitrophenol (ANP) in two hair dyeing formulations was investigated after application to the skin of rats. After 1 and 5 days, 0.21 and 0.36%, respectively, of the administered radioactivity was absorbed from formulation 1 which contained carboxymethylcellulose as a thickening agent. Absorption was greater (1.12% after 1 day, 1.67% after 5 days) from formulation 2 which contained oleic acid and isopropanol. Complementary studies of absorption after administration of [14C]ANP by sc injection or oral gavage were also carried out. The radioactivity was rapidly excreted, predominantly in the urine, in both cases. Biliary excretion was also detected in an oral study.

Cutaneous penetration of some hairdyes in the hairless rat

The cutaneous penetration of certain number of oxidation dyestuffs for hair [p-aminophenol, 2,4-diaminoanisole, 2,4-diaminophenoxyethanol, resorcinol, 3-acetylamino-2,6-dimethylphenol and the indamine: N-(4'-hydroxyphenyl)-3-amino-6-methylbenzoquinoneimine], either alone or when formulated with other dyestuffs, and under various experimental conditions, has been evaluated in the hairless rat using C14 labeled molecules. It has been found that: Dyestuffs having indamine structures, formed by oxidation of their precursors (bases, couplers), for all practical purposes do not cross the cutaneous barrier. No fixation of those dyestuffs investigated (resorcinol, 2,4-diaminoanisole, 2,4-diaminophenoxyethanol) which do pass through the cutaneous barrier is found in either liver or thyroid of the experimental animals, 4 days after their topical application. The amount of the hairdye 3-acetylamino-2,6-dimethylphenol which penetrates the cutaneous barrier is constant for quantities of hairdye solution greater than or equal to 20 mg/cm2 of skin. The type and composition of the excipient used in the formulation of hairdyes plays an important role in their penetration.