Hair regrowth products

I have a question regarding the use of hair regrowth products. One of my roommates (who is Muslim) suffers from some very serious balding (at a very young age) and he has begun using a hair regrowth shampoo.  I have also heard of other Muslim men using products like rogaine, medicines (pills and so forth) and even getting hair transplants.  So, I want to know if this is okay, Islamically?  If not, why?

In the Name of Allah, Most Compassionate, Most Merciful,

Firstly, if the products which are used for treating baldness (such as creams and ointments) do not have any impure or unlawful substance in them, then it is permissible to use them.

Secondly, it is generally understood that hair transplantation is the redistribution of your naturally growing hair. Hair follicles growing at the back of the head are transplanted to the bald areas. This method of hair transplantation is permissible as long as it only used for treating baldness and not for beautification.

It should be also remembered here that it is not permitted to use the hair of another human. The Messenger of Allah (Allah bless him & give him peace) clearly forbade that the hair of one person be used by another (See the major Hadith collections). However, there is a dispensation in using the hair of other then a human, when there is a genuine need (as described above).

And Allah knows best
Muhammad ibn Adam al-Kawthari