This product cannot be shipped to Israel, the United States and Japan. There are many thoughts on what causes dandruff. There is however, only one real answer. It is now known that dandruff is primarily caused by a fungus known as Pityrosporum ovale (P. ovale). Scientists may also call it malassezia furfur. Before you recoil in disbelief, you should know that this fungus is a naturally occurring organism found on everybody's scalp and in most cases poses no problem at all. However, under certain circumstances, P. Ovale can proliferate, irritating the scalp and depleting it of it's nutrients. When this occurs, dead cells are shed from the scalp faster – flaking and itching are the result. This condition is known as dandruff. What makes Nizoral unsurpassed as a dandruff treatment? Put simply, Nizoral treats the cause of dandruff – excess of P. ovale found on your scalp. Whilst some other treatments are busy treating only the symptoms, Nizoral goes to work on the cause. In fact, the active ingredient in Nizoral has been clinically proven to be your best defence against P. Ovale. This gentle, active ingredient also binds to the natural protein in your hair called keratin. So it keeps working for days after you have stepped out of the shower. The importance of binding with keratin. Most active ingredients found in other dandruff shampoos lack the ability to bind with the keratin found in your hair. Unfortunately, this means that when rinsing the shampoo out the active ingredient is also going down the drain. Even worse, this allows the P.Ovale to re-colonise the scalp. That is why when using these shampoos you need to wash your hair on a daily basis. Thankfully, Nizoral has a strong affinity for keratin and actually binds with the scalp and hair shafts. Therefore, you only have to use Nizoral twice a week. Continued use just twice a week will keep dandruff from returning