Dandruff is harmless. But that's no consolation if people call you Commander Whitehead behind your bespeckled back and shoulders. Dandruff (or seborrheic dermatitis, in medical terms) affects the scalp and eyebrows--areas of the skin where oil glands are most active--leaving them oily and flaky. Unchecked, dandruff can collect around your ears and cascade down your neck and back.

While dandruff seems to run in families, no one knows exactly what causes it. Possible contributing factors include:

• Stress
• Infrequent shampooing
  
• Oily skin in general
  
• Extremes in weather (hot and humid or cold and dry conditions)

Whatever the cause of your dandruff, thorough, daily shampooing is the most successful home treatment, To make shampooing more effective:

• Scrub thoroughly to loosen scaly skin, but be gentle, taking care not to scratch or irritate the scalp and increase the risk of infection.
  
• Use an antidandruff shampoo. Over-the-counter shampoos that contain selenium sulfide are often effective for mild cases. More severe dandruff may require a prescription medication containing coal tar or a scalp lotion with cortisone, which is rubbed into the scalp.