Animal-derived collagen and Islamic religious prescriptions: a systematic review.

Collagen, predominantly porcine (~ 41% of global production), is a ubiquitous pharmaceutical, cosmetic, and biomedical excipient. For the estimated 1.9 billion Muslim patients worldwide, this raises a recurrent concern with potential implications for medication adherence and patient counselling, including in rheumatology. This PRISMA 2020-compliant systematic review synthesises 56 studies retrieved from five databases (initial yield 1035 records), addressing four domains: Islamic jurisprudential classification by source, validated analytical authentication, halal-compliant alternatives, and international regulatory frameworks. Analytical studies were appraised with a modified QUADAS-2, jurisprudential sources with an internal-consistency checklist, certainty of evidence with a GRADE-informed framework. Across mainstream Sunni jurisprudence, porcine collagen is classified as prohibited (haram) regardless of industrial processing, with high inter-school agreement and convergent classical and contemporary fatwa support; bovine collagen is conditionally permissible subject to ritual (zabiha) slaughter and certified traceability; fish collagen is broadly accepted and is the most commercially mature alternative. Quantitative PCR (LOD ≈0.01%) offers the best balance of sensitivity and validation for native matrices, while LC-MS/MS proteomics is preferable for extensively hydrolysed products; orthogonal testing is advisable where stakes are high. Recombinant collagen offers the highest theoretical halal assurance but is constrained by cost, regulatory translation, and substrate certification. International harmonisation of halal pharmaceutical standards comparable to Malaysia's MS 2424:2019 is identified as a regulatory gap. Findings are most directly relevant to pharmacists, regulators, and clinicians serving Muslim populations; direct rheumatology-specific evidence remains limited and warrants dedicated study.