The investigators will collect a single saliva, urine and blood specimen from children with asthma and sickle cell disease, children with sickle cell disease only, and African American children with asthma only for metabolomic analysis. A single urine sample will be collected from health African American children without any chronic diseases. Blood will be stored for a future study to compare metabolomic variability between blood and urine. The investigator's goal is to use this information to correctly identify children with asthma. These data will enhance the investigator's understanding of the mechanisms that underlie the molecular asthma phenotype in sickle cell disease, which should lead to more targeted treatment of asthma in sickle cell disease. The investigators long-term goal is to reduce the burden of asthma in the child with sickle cell disease (pain, ACS, and death) by using this innovative systems biology approach.