| Peptide Therapy: Benefits, And Side Effects Explained Are There Any Known Side Effects of Peptide Therapy? While peptide therapy is generally considered safe, some patients report mild side effects such as localized swelling, redness at the injection site, or transient fatigue. In rare cases, individuals may experience allergic reactions or bruising. Most adverse events are short‑term and resolve without intervention. What is Peptide Therapy? Peptide therapy involves |