There is currently no strong evidence to suggest that BCAAs (branched-chain amino acids) cause acne. While BCAAs can affect hormone levels in the body, which can sometimes be a factor in the development of acne, the evidence linking BCAAs and acne is limited and inconclusive.
That being said, some people may experience skin irritation or breakouts from certain ingredients found in BCAA supplements, such as artificial sweeteners or other additives. If you have sensitive skin or are prone to acne, it may be a good idea to choose a BCAA supplement that is free from these ingredients, or to talk to a healthcare professional for advice.
Overall, BCAAs are generally considered safe and are not typically associated with acne or other skin issues. As with any supplement, it's important to pay attention to your body's response and to talk to a healthcare professional if you have any concerns.