Ramsay Hunt syndrome, Bell's palsy and dehydration. Those most at risk are children with cancer, notably leukemia - the most common of all childhood cancers. The immune response of a child with cancer is not only impaired by their disease, but also by the cancer treatment - radiotherapy and chemotherapy given to destroy proliferating cancer cells also damage the cells of the immune system. In immunocompromised patients, the incubation period for varicella is shorter, the rash spreads more rapidly, and lesions continue to appear for 10 days or more. The rash is also more extensive, with lesions more prominent on the extremities and often developing on the palms of the hands and the soles of the feet.
Healing takes longer, fever is more severe and complications are more common.
The risk of varicella to immunocompromised individuals was demonstrated in the 1970s in a study of children receiving chemotherapy.