Occurring deeper in the outer layer of skin (epidermis), miliaria rubra is sometimes called prickly heat. Adults usually develop miliaria rubra after they're exposed to hot, humid weather or if they're confined to bed rest. Infants usually develop this type of heat rash between the first and third weeks of life. Signs and symptoms typically include:
A less common form of heat rash, miliaria profunda occurs mainly in adults who have had repeat bouts of miliaria rubra. It affects the dermis, a deeper layer of skin, and appears soon after exercise or any activity that causes sweating. Signs and symptoms may include:
Heat rash usually heals on its own and doesn't require medical care. See your doctor if you or your child has symptoms that last longer than a few days, the rash seems to be getting worse, or there are signs of infection, such as:
Heat rash can also occur in people who are confined to a hospital bed for long periods, especially if they have a fever.
No tests are needed to diagnose heat rash; your doctor can determine the problem with a visual exam.