This chapter presents a glossary of common paediatric problems and disorders starting with the alphabet “H”. This glossary covers the following topics: Head lice; hearing impairment; heart failure; hernia, congenital diaphragmatic (CDH); hernias; Hirschsprung disease; human immunodeficiency virus (HIV); hydrocephalus; hyperthyroidism; hypoglycaemia in neonates; hypospadias; and hypoxic‐ischaemic encephalopathy (HIE). For each topic, the chapter provides quick access to information on their signs, symptoms, aetiological agents, complications, treatment and management. The louse bite of head lice introduces enzymes, an anti‐clotting agent and a local anaesthetic into the scalp. This produces a typical allergic reaction in children. CDH is a congenital defect in the formation of the diaphragm that leads to the protrusion of abdominal contents into the thoracic cavity. Infants may have a history of polyhydramnios. Nasogastric tube (NGT) is used to decompress the bowel. If respiratory support is indicated, should be via endotracheal tube (ETT) and mechanical ventilation with avoidance of high peak inspiratory pressures.