**Core Concept**
Steven Johnson Syndrome (SJS) is a severe, life-threatening cutaneous adverse reaction often triggered by medications, involving epidermal necrosis, mucosal involvement, and systemic symptoms. It is typically mediated by HLA alleles and immune activation, with certain drugs being well-established risk factors.

**Why the Correct Answer is Right**
Paracetamol (acetaminophen) is not associated with SJS and is one of the safest analgesics in terms of adverse drug reactions. In contrast, cephalosporins (especially first-generation), carbamazepine (an anticonvulsant), and ibuprofen (a NSAID) have been documented in case reports and pharmacovigilance databases as causing SJS, particularly in genetically susceptible individuals. The mechanism involves drug-induced immune activation or direct cytotoxicity, with carbamazepine being a known high-risk agent due to HLA-B*15:02 allele association.

**Why Each Wrong Option is Incorrect**
Option A: Cephalosporins — Particularly first-generation (e.g., cefalexin), are well-known SJS triggers, especially in patients with specific HLA types.
Option B: Ibuprofen — Though less common, NSAIDs like ibuprofen have been linked to SJS, especially in high-dose or prolonged use.
Option C: Carbamazepine — A well-established cause of SJS, with strong epidemiological and genetic evidence (HLA-B*15:02).

**Clinical Pearl / High-Yield Fact**
Always consider SJS in patients with sudden rash, mucosal involvement, and fever after starting a new medication. Avoid first-generation cephalosporins and carbamazepine in patients with HLA-B*15:02 allele, especially in Asian populations. Paracetamol remains safe and is not a known trigger.

✓ Correct Answer: D. Paracetamol