Thnk I can chime in here:
When beta alanine binds to the nerve receptors it causes that tingling feeling, it usually happens within 15-20 minutes of taking Jack3d. This is when I know I am ready to get get goin'. The sensation is called paraesthsia.
par·es·the·sia (noun) a sensation of pricking, tingling, or creeping on the skin having no objective cause and usually associated with injury or irritation of a sensory nerve or nerve root
From everything I have read there is no negative side effects from this reaction. In time this feeling will start to fade but the carnosine absorption will still be just as effective.
I happen to like it...one of the few supplements in my opinion that you can really feel working.
Hope that helps