McCune-Albright syndrome (MAS) is a syndrome caused by a genetic mutation that causes a specific protein in the body called a G protein to be constantly active. Children with McCune-Albright syndrome classically have early puberty, areas of increased skin pigmentation, and bone lesions resulting from the constant activity of the specific protein involved. Histamines are known to play a role in allergies and related allergic problems. The effects of histamines are controlled by the same G protein that is overly active in McCune-Albright syndrome. Thus, one could predict that patients with McCune-Albright may be at high risk for allergic problems. To date, no studies have documented any form of histamine excess or allergic difficulties in patients with McCune-Albright syndrome. However, the investigators have made the observation that a high percentage of their patients with MAS exhibit a range of allergic symptoms, from mild symptoms, to severe, life-threatening symptoms. The purpose of this study is to demonstrate increased histamine response by using a histamine skin test in patients with MAS. If increased reactions to histamines can be documented in MAS patients when compared to controls, severe and potentially life threatening allergic reactions in children with MAS could be anticipated and avoided.