For Ken:
H&S 'Classic Clean' shampoo contains:
Aqua, Sodium Lauryl Sulfate, Sodium Laureth Sulfate, Glycol Distearate, Zinc Carbonate, Sodium Chloride, Sodium Xylenesulfonate, Zinc Pyrithione, Cocamidopropyl Betaine, Dimethicone, Parfum, Sodium Benzoate, Guar Hydroxypropyltrimonium Chloride, Hydrochloric Acid, Hexyl Cinnamal, Linalool, Sodium Hydroxide, Magnesium Carbonate Hydroxide, Magnesium Nitrate, Sodium Polynaphthalenesulfonate, Methylchloroisothiazolinone, Magnesium Chloride, CI 42090, Methylisothiazolinone, CI 17200
H&S 'Men Ultra Hair Booster Anti-Dandruff' shampoo contains:
Aqua, Sodium Lauryl Sulfate, Sodium Laureth Sulfate, Glycol Distearate, Zinc Carbonate, Sodium Chloride, Sodium Xylenesulfonate, Zinc Pyrithione, Cocamidopropyl Betaine, Dimethicone, Parfum, Sodium Benzoate, Menthol, Guar Hydroxypropyltrimonium Chloride, Hydrochloric Acid, Caffeine, Sodium Hydroxide, Magnesium Carbonate Hydroxide, Limonene, Linalool, Magnesium Nitrate, Sodium Polynaphthalenesulfonate, CI 19140, Methylchloroisothiazolinone, Magnesium Chloride, Methylisothiazolinone, CI 42090
Given that things like 'CI 17200' are simply colourings, there seems to be no real difference except for the price. (Forget Head & Shoulders anyway. Supermarket 'own brand' anti-dandruff shampoos are just as good and usually cost a great deal less).