 Shingles is an infection commonly seen in children with a weakened immune system immunocompromised children. The immune system can be weakened as a result of medications that patients receive for cancer or other serious illness or as a result of a bone marrow transplantation. Shingles in children with a weakened immune system may spread throughout the body and in some instances may be life-threatening. Acyclovir is a medication that is routinely used to treat immunocompromised children with shingles in order to prevent further spread of their shingles and to help them heal faster. Acyclovir is also given to bone marrow transplant patients to prevent reactivation of HSV infection. 