When your hair is shiny, you can credit the cuticle. The cuticle is the protective outer layer on each strand of hair. Cuticle cells lie in an overlapping, shingle-like fashion. On a healthy head, they're flat and snug, forming an even surface that reflects light for that desirable sheen. A cuticle can be damaged, however, by excessive washing that strips away sebum and intensive styling that involves heat, creams and gels. Damaged cuticles resemble a roof after a windstorm -- torn and rough, with some shingles loose and others missing. They're prone to snags and tangles, which means more combing, which can lead to more breakage.
Conditioning products contain ingredients that smooth and seal the cuticle. This not only improves the surface, but also helps to keep out moisture. Like water that seeps into a roof, water that seeps into a damaged cuticle can worsen the problem. Conditioners also help prevent strands from tangling.
Shampoos typically have built-in conditioners, which may be enough for your hair. If you use a separate product, you may want to experiment with different brands and ingredients. But be aware that conditioning can be overdone. Conditioning agents can build up with regular use, leaving hair limp and -- ironically -- dull. Fortunately, there are shampoos to remedy that problem, too. Clarifying or deep-cleansing shampoos, also called volumizers, are designed to wash away built-up styling products and restore body.