Immunosuppressive drugs are normally used in transplant surgery to stop the immune system from rejecting the transplanted organ. It is thought that the same drugs should be able to suppress the immune systems action against the hair follicles which is considered to be the way in which Alopecia areata occurs.

The main drug used in preventing organ rejection is cyclosporin, this has been shown to be effective in regrowing hair lost due to Alopecia areata when it is taken systematically, however appears to have very little effect when applied topically.

The main problem with taking immunosuppressive drugs systematically is that it can led to a lowered resistance to infection and also leave patients more open to the possibility of tumors.