That peptide reaction youre panicking about? , Red welts. Itching. Flushing., In most cases, this isnt an allergic reaction its mast cell activation., Your body was already inflamed, stressed, or Mounjaro (Tirzepatide) Side Effects: Your Month by Month Guide Dosing Schedule, Injection Sites 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 CJC 1295 Ipamorelin: The Benefits of Peptide Therapy Oasis Health and Medicine