The first aid for burns is to run cold water over the burn for 20 minutes. This is effective for up to three hours after the injury. Assess the affected body surface area using the rule of nines. Consult a burn unit if more than 5% of the total body surface area is burnt in a child or if more than 10% in an adult. Extensive or deep burns and burns to special areas, such as the hands, should be referred. Chemical or electrical burns should also be assessed by a burn unit. For minor burns, antimicrobial dressings are recommended, but oral antibiotics should be avoided unless there are signs of infection. As burns are tetanus prone, check the patient's immunisation status. Burns that become infected or are slow to heal should be discussed with a burn unit. The burn unit can also provide advice if there are uncertainties about how to manage a patient.