Viral Exanthem: This is the most common cause of a whole body rash in children, often associated with viral infections such as measles, rubella, or roseola. The rash typically appears after a prodrome of fever and upper respiratory symptoms.

Atopic Dermatitis (Eczema): A chronic skin condition characterized by itchy, inflamed skin. It can present as a whole body rash, especially if the child has a history of allergies or asthma.
Contact Dermatitis: An allergic reaction to substances like poison ivy, oak, or sumac, or irritants such as soaps or detergents, which can cause a widespread rash.
Impetigo: A highly contagious bacterial skin infection that can spread across the body, often starting as a localized lesion.

Meningococcemia: A life-threatening infection caused by Neisseria meningitidis, which can present with a petechial or purpuric rash. Early recognition and treatment are crucial.
Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis: Severe skin and mucous membrane disorders, usually a reaction to medications or infections, which can be fatal if not promptly treated.
Kawasaki Disease: An acute febrile illness that can cause a rash, along with other symptoms like fever, conjunctivitis, and lymphadenopathy. It requires early diagnosis to prevent cardiac complications.

Pityriasis Rubra Pilaris: A rare skin disorder characterized by a reddish-orange rash and scaling, often involving the whole body.
Staphylococcal Scalded Skin Syndrome (SSSS): A condition caused by staphylococcal toxins that can lead to widespread skin exfoliation, more common in younger children.
Juvenile Rheumatoid Arthritis (JRA): A chronic autoimmune disease that can present with a rash, fever, and joint inflammation, among other symptoms.