Keratin

The keratin is a protein made up of long chains of amino acids, which are interposed various vitamins and trace elements.
Widespread throughout the animal kingdom, in the keratin is the main constituent of hair, hair and nails.  The same protein is, for example, in the composition of the bristles of pigs, cow’s hooves, horns of rhinoceros, wool and feathers of birds.
Although it contained many different kinds of amino acids, the keratin is especially rich in an amino acid called cysteine sulfide.  Thanks to the various atoms of sulfur, chains of keratin may maintain close cohesion, wrap in a structure resembling a propeller.  It is these ties, these disulphide bridges, and to ensure the rigidity and strength of hair, nails and hair.
Being very resistant to proteolysis enzymes in our stomach and intestine, the keratin is devoid of any property or nourishing aphrodisiac.  For this reason the use of rhinoceros horn to awaken dormant desires is absolutely devoid of science.
The strength of keratin may be undermined by the prolonged use of chemicals, such as those contained in hair dyes or shampoos more aggressive.  Even exposure to air pollutants, physical treatment (permanent, plate, hair dryer too hot), some medications, stress and a long list of diseases, can lead to degradation of the structure of hair keratin.