I haven’t personally seen a ton of Cartalax-specific side effect info, but itching can happen with peptide injections in general. If it’s just near the injection site, it could be irritation from the shot, bac water, concentration, or skin sensitivity. If it’s more full-body itching, hives, rash, swelling, chest tightness, dizziness, or breathing changes, I’d stop and treat it like a possible reaction.
Same thing as happening to me I wasn’t sure if it was my BAC water because when reconstituted Cartalax I used a brand new BAC water for the first time. So far very itchy, but going to push through the 20 days.