The UN children's agency has appealed for nearly $32 million to assist millions of children and women in Kenya, Somalia, Ethiopia and Djibouti.
"Half a million of those children are facing imminent life-threatening conditions, with long lasting consequences to their physical and mental development," Unicef said in a statement.
This crisis is being called the worst in 50 years, in a region familiar with severe drought.
"Unicef estimates a total of 10 million people are already in need of humanitarian assistance. High food prices and prolonged drought are worsening an already dire situation for thousands of families in need of food and water," the statement added.
The Horn of Africa includes Eritrea, Ethiopia, Somalia, Djibouti, Kenya countries.