What it's actually good for
Beta-alanine is one of the few sports supplements with genuinely strong evidence, but only for a specific type of exercise. It works by increasing intramuscular carnosine, which buffers the hydrogen ions that accumulate during high-intensity effort and contribute to the "burn" that limits performance. Supplementation raises muscle carnosine by 40-80% over several weeks, and this consistently translates to improved performance in efforts lasting roughly 1-4 minutes — think 400-800m running, high-rep sets, rowing intervals, or repeated sprints.
The key nuance is specificity. If your sport or training involves sustained high-intensity work in that 1-4 minute window, beta-alanine is well-supported. For pure strength work (very short efforts), long endurance (aerobic-dominant), or general health, the evidence is weak to nonexistent. The tingling sensation (paresthesia) that many people experience is harmless but can be startling if unexpected — splitting your daily dose into smaller portions or using a sustained-release form eliminates it. Unlike some supplements that show acute effects, beta-alanine requires consistent daily loading over at least 2-4 weeks to build up carnosine stores before you will notice anything.