Differential Diagnosis for Full Body Itchy Red Rash
Single Most Likely Diagnosis
- Allergic Contact Dermatitis: This is a common condition that occurs when the skin comes into contact with an allergen, causing an immune reaction. The rash often starts at the site of contact and can spread. Given the description of the rash starting on the stomach and moving to other parts of the body, this could be a likely explanation, especially if the patient has recently introduced new products or substances to their skin.
Other Likely Diagnoses
- Atopic Dermatitis (Eczema): Characterized by itchy, inflamed skin, atopic dermatitis can present with a widespread rash. It often starts in childhood but can persist into adulthood. The pattern of spread from the stomach to other areas could fit, especially if the patient has a history of atopic diseases.
- Urticaria: Also known as hives, urticaria can cause itchy red welts that can appear anywhere on the body. While it typically doesn't spread in the linear fashion described, it's possible for new hives to appear as old ones fade, giving the appearance of movement.
- Drug Rash: Many medications can cause skin reactions, ranging from mild to severe. A drug rash can appear anywhere on the body and might start in one area before spreading, depending on the drug and individual reaction.
Do Not Miss Diagnoses
- Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN): These are severe skin conditions usually triggered by medications. They can start with a rash that spreads and can be life-threatening. Early recognition is crucial for treatment and preventing further complications.
- Erythema Multiforme: This is an immune-mediated disorder that can be triggered by infections or medications. It's characterized by target lesions and can be widespread. While less common, it's a condition that should not be missed due to its potential severity.
Rare Diagnoses
- Pityriasis Rubra Pilaris (PRP): A rare skin disorder characterized by constant scaling, redness, and thickening of the skin. It can start with a Herald patch and then spread, though the pattern described doesn't perfectly match the typical presentation of PRP.
- Cutaneous T-Cell Lymphoma (CTCL): A type of skin cancer that can cause a variety of skin symptoms, including patches, plaques, and tumors. While rare, it's a diagnosis to consider in cases of unexplained, persistent rashes, especially if they are resistant to standard treatments.