The handmade rugs are from natural wool and sometimes a mixture of wool and silk. In most Persian rugs, the pile is of sheep's wool. Its characteristics and quality vary from each area to the next. It depends on the breed of sheep, climatic conditions, pasturage, and also the particular customs relating to when and how the wool is sheared and processed. The wool of higher grades of Persian wool rugs are Kurk, or Kork. The Kurk is gained from the wool growing on the sheep's neck.
The Traditional dyes they use for these rugs are usually from plants. They add dye stuffs to the yarn, which remains in the dyeing solution for a defined time. Then they leave dyed yarn to dry, exposed to air and sunlight. These are the facts that prevent allergic reactions comparing the synthetic machine made ones.

The weaving of pile rugs is a time-consuming process which, depending on the quality and size of the rug, may take anywhere from a few months to several years to complete. That is why the Persian handmade carpet and rugs are washable. Hence they are of natural material, you can wash them again and again. Against the machine made rugs which washing them would shorten their life, washing hand made rugs never harm them. Every time you clean these rugs, it seems you are having new ones.
As a result, buying hand made rugs could be kind of investing money. Finally, you are not going to lose money as Persian rugs will get more expensive during the years.