Q: Why can peptides sometimes cause flushing, itching, or redness?, A: Because some peptides can turn that alarm up too fast., This can happen when:, The dose is high, The body absorbs it quickly, Peptide injections can sometimes cause redness or itching at the injection site, but most of the time this is not a true allergy. In the skin, we have mast cells that contain histamine. These cells Drug Rash and Eruption: Symptoms, Pictures, Causes, and Treatment Rupatadine to prevent local allergic reactions to sublingual allergy immunotherapy: a case series Allergy, Asthma & Clinical Immunology Springer Nature Link