Rash is a common complaint, particularly during infancy. Most rashes are not serious.
Rashes can be caused by infection (viral, fungal, or bacterial), contact with irritants, atopy, drug hypersensitivity, other allergic reactions, inflammatory conditions, or vasculitides (see Table: Some Causes of Rash in Infants and Children Some Causes of Rash in Infants and Children Rash is a common complaint, particularly during infancy. Most rashes are not serious. Rashes can be caused by infection (viral, fungal, or bacterial), contact with irritants, atopy, drug hypersensitivity... read more ).
Overall, the most common causes of rash in infants and young children include
Numerous viral infections cause rash. Some (eg, chickenpox Chickenpox Chickenpox is an acute, systemic, usually childhood infection caused by the varicella-zoster virus (human herpesvirus type 3). It usually begins with mild constitutional symptoms that are followed... read more , erythema infectiosum Erythema Infectiosum Erythema infectiosum, acute infection with parvovirus B19, causes mild constitutional symptoms and a blotchy or maculopapular rash beginning on the cheeks and spreading primarily to exposed... read more , measles Measles Measles is a highly contagious viral infection that is most common among children. It is characterized by fever, cough, coryza, conjunctivitis, an enanthem (Koplik spots) on the oral mucosa... read more ) have a fairly typical appearance and clinical manifestation; others are nonspecific. Cutaneous drug reactions Drug Eruptions and Reactions Drugs can cause multiple skin eruptions and reactions. The most serious of these are discussed elsewhere in THE MANUAL and include Stevens-Johnson syndrome and toxic epidermal necrolysis, hypersensitivity... read more are usually self-limited maculopapular exanthems, but sometimes more serious reactions occur.
Uncommon but serious causes of rash include
History of present illness focuses on the time course of illness, particularly the relationship between the rash and other symptoms.
Review of systems focuses on symptoms of causative disorders, including gastrointestinal symptoms (suggesting immunoglobulin A–associated vasculitis [formerly called Henoch-Schönlein purpura] or hemolytic-uremic syndrome), joint symptoms (suggesting immunoglobulin A–associated vasculitis or Lyme disease), headache or neurologic symptoms (suggesting meningitis or Lyme disease).
Past medical history should note any drugs recently used, particularly antibiotics and anticonvulsants. Family history of atopy is noted.
Examination begins with a review of vital signs, particularly to check for fever. Initial observation assesses the infant or child for signs of lethargy, irritability, or distress. A full physical examination is done, with particular attention to the characteristics of the skin lesions Description of Skin Lesions An extensive language has been developed to standardize the description of skin lesions, including Lesion type (sometimes called primary morphology) Lesion configuration (sometimes called secondary... read more , including the presence of blistering, vesicles, petechiae, purpura, or urticaria and mucosal involvement. Children are evaluated for meningeal signs (neck stiffness, Kernig and Brudzinski signs), although these signs are often absent in children < 2 years.
Well-appearing children without systemic symptoms or signs are unlikely to have a dangerous disorder. The appearance of the rash typically narrows the differential diagnosis. The associated symptoms and signs help identify patients with a serious disorder and often suggest the diagnosis (see Table: Some Causes of Rash in Infants and Children Some Causes of Rash in Infants and Children Rash is a common complaint, particularly during infancy. Most rashes are not serious. Rashes can be caused by infection (viral, fungal, or bacterial), contact with irritants, atopy, drug hypersensitivity... read more ).
Bullae and/or sloughing suggest staphylococcal scalded skin syndrome Staphylococcal Scalded Skin Syndrome Staphylococcal scalded skin syndrome is an acute epidermolysis caused by a staphylococcal toxin. Infants and children are most susceptible. Symptoms are widespread bullae with epidermal sloughing... read more or Stevens-Johnson syndrome Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) Stevens-Johnson syndrome and toxic epidermal necrolysis are severe cutaneous hypersensitivity reactions. Drugs, especially sulfa drugs, antiseizure drugs, and antibiotics, are the most common... read more and are considered dermatologic emergencies. Conjunctival inflammation may occur in Kawasaki disease Kawasaki Disease Kawasaki disease is a vasculitis, sometimes involving the coronary arteries, that tends to occur in infants and children between the ages of 1 year and 8 years. It is characterized by prolonged... read more , measles Measles Measles is a highly contagious viral infection that is most common among children. It is characterized by fever, cough, coryza, conjunctivitis, an enanthem (Koplik spots) on the oral mucosa... read more , staphylococcal scalded skin syndrome, and Stevens-Johnson syndrome. Any child presenting with fever and petechiae or purpura must be evaluated carefully for the possibility of meningococcemia Meningococcal Diseases Meningococci (Neisseria meningitidis) are gram-negative cocci that cause meningitis and meningococcemia. Symptoms, usually severe, include headache, nausea, vomiting, photophobia, lethargy,... read more . Bloody diarrhea with pallor and petechiae should raise concern about the possibility of hemolytic uremic syndrome Thrombotic Thrombocytopenic Purpura (TTP) Thrombotic thrombocytopenic purpura (TTP) is an acute, fulminant disorder characterized by thrombocytopenia and microangiopathic hemolytic anemia. Other manifestations may include alterations... read more . Fever for > 5 days with evidence of mucosal inflammation and rash should prompt consideration of and further evaluation for Kawasaki disease.
For most children, the history and physical examination are sufficient for diagnosis. Testing is targeted at potential life threats; it includes Gram stain and cultures of blood and cerebrospinal fluid for meningococcemia; complete blood count, renal function tests, and stool tests for hemolytic uremic syndrome).
Treatment of rash is directed at the cause (eg, antifungal cream for candidal infection).
For diaper rash, the goal is to keep the diaper area clean and dry, primarily by changing diapers more frequently and gently washing the area with mild soap and water. Sometimes a barrier ointment containing zinc oxide or vitamins A and D may help.
Pruritus in infants and children can be lessened by oral antihistamines:
Diphenhydramine: For children > 6 months, 1.25 mg/kg every 6 hours (maximum 50 mg every 6 hours)
Hydroxyzine: For children > 6 months, 0.5 mg/kg every 6 hours (maximum for children < 6 years, 12.5 mg every 6 hours; for those ≥ 6 years, 25 mg every 6 hours)
Cetirizine: For children 6 to 23 months, 2.5 mg once a day; for those 2 to 5 years, 2.5 to 5 mg once a day; for those > 6 years, 5 to 10 mg once a day
Loratadine: For children 2 to 5 years, 5 mg once a day; for those > 6 years, 10 mg once a day
Some common adverse effects of antihistamines include dry mouth, drowsiness, dizziness, nausea and vomiting, restlessness or moodiness (in some children), urinary hesitancy, blurred vision, and confusion.