Contact Dermatitis: This is a common condition that can occur after surgery due to irritation from surgical tapes, antiseptics, or other products used during or after the procedure. The rash typically appears as red, itchy, and blistered skin.

Allergic Reaction to Medication: Patients may develop an allergic reaction to antibiotics or other medications prescribed post-operatively, leading to a rash.
Surgical Site Infection: Although less common, a rash could be a sign of a surgical site infection, especially if accompanied by other symptoms like increased redness, swelling, warmth, or purulent discharge.
Urticaria: Hives can occur due to allergic reactions or as a response to stress, including surgical stress.

Necrotizing Fasciitis: A severe and potentially life-threatening infection that requires immediate attention. Early signs can include redness, swelling, and pain out of proportion to the expected post-surgical discomfort, which might initially present as a rash.
Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN): Although rare, these are severe skin conditions usually triggered by medications. They can start with a rash and progress to widespread skin necrosis and detachment, which is life-threatening.

Erythema Multiforme: An immune-mediated disorder that can be triggered by infections or medications, characterized by target-like lesions on the skin.
Fixed Drug Eruption: A type of drug reaction that recurs at the same site each time the drug is taken, appearing as well-defined, circular patches.
Autoimmune Disorders: Conditions like lupus or rheumatoid arthritis can sometimes be triggered or unmasked by surgical stress, presenting with a rash among other symptoms.