Stevens-Johnson Syndrome (SJS): This is the most likely diagnosis given the presentation. SJS is a severe skin and mucous membrane disorder, usually a reaction to medication or infection, characterized by a rash, blisters, and skin peeling, which matches the description provided.

Toxic Epidermal Necrolysis (TEN): TEN is closely related to SJS and can present similarly, with widespread skin necrosis and detachment. The distinction between SJS and TEN can be based on the extent of skin involvement, with TEN being more severe.
Erythema Multiforme (EM): EM is an immune-mediated disorder that can present with skin lesions similar to SJS but typically lacks the severe mucosal involvement and widespread skin detachment seen in SJS.
Drug Rash with Eosinophilia and Systemic Symptoms (DRESS): DRESS syndrome is a severe drug reaction that can mimic SJS, with rash, fever, lymphadenopathy, and internal organ involvement, but it tends to have a more gradual onset.

Staphylococcal Scalded Skin Syndrome (SSSS): Although less common in adults, SSSS can present with widespread skin peeling and erythema, similar to SJS. It is caused by staphylococcal toxins and can be life-threatening if not promptly treated.
Toxic Shock Syndrome: This condition, caused by bacterial toxins, can present with a rash, fever, and multi-organ failure. It is critical to identify and treat promptly due to its high mortality rate.

Paraneoplastic Pemphigus: A rare autoimmune disorder associated with underlying neoplasms, characterized by severe mucosal lesions and skin blistering, which can resemble SJS.
Graft-Versus-Host Disease (GVHD): In patients with a history of bone marrow or stem cell transplantation, GVHD can cause skin manifestations that might mimic SJS, including rash and skin blistering.
Autoimmune Disorders (e.g., Lupus, Pemphigus): Certain autoimmune conditions can present with skin manifestations that might be confused with SJS, including rashes and blistering lesions.