Physical symptoms of lead poisoning in both children and adults include cramping, constipation or diarrhea, excessive fatigue, headache, nausea, and muscle weakness. Behavioral symptoms of lead poisoning in children include irritability, learning problems, hyperactivity, loss of appetite, and aggressiveness. Behavioral symptoms in adults include irritability, unexplained mood changes, changes in sleep patterns, inability to concentrate, and memory loss. Neurological symptoms of lead poisoning include poor coordination, weakness in the hands and feet, seizures, paralysis and coma. Symptoms of lead poisoning usually do not present until the level of lead in the blood is already excessive. Most lead poisoning happens over an extended period of time.