A Food and Drug Administration advisory committee hearing on Thursday and Friday may set Health and Human Services Secretary Robert F. Kennedy Jr., known for embracing unproven wellness trends, on a collision course with agency scientists who have deep expertise on drug safety.

At issue is whether the F.D.A. should allow specialized pharmacies to produce seven peptide injections that the agency banned three years ago over safety concerns. The injections, some of which Mr. Kennedy has used and trumpeted, are currently sold as “research grade” products not meant for widespread use. Despite the restriction, they are marketed online for a wide range of claimed benefits, from tendon repair to brain health.

In documents prepared for the hearing, F.D.A. scientists advise against allowing broader use, saying that the risks and benefits of the peptide drugs under consideration are poorly understood and have not been sufficiently studied.

The committee evaluating that data and other information includes a traditional roster of pharmacists and academic scientists and doctors — but also six people who sell or dispense peptides. F.D.A. advisory panels are intended to be neutral bodies of outside experts; it is highly unusual to appoint people to them who market the products that they are voting on.

“There seems to be a fingerprint of R.F.K. on this committee, is my impression,” said Paul Knoepfler, a University of California at Davis biologist who studies F.D.A. oversight of unproven treatments. He added: “To me, the makeup of this committee seems pretty striking.”

In an initial pair of votes on Thursday, the six peptide sellers joined with a compounding pharmacist and a pharmacy business executive to vote in favor of adding a peptide known as BPC-157 to a list of products that bespoke pharmacies can dispense.