Gamma-aminobutyric acid (GABA) is a naturally-occurring neurotransmitter, a chemical which transmits nerve impulses in the brain. Some people take GABA as a nutritional supplement for various claimed benefits. Side effects are uncommon and mild.
GABA supplements are said to enhance mood and relaxation, improve sleep, relieve anxiety and stress and improve concentration. GABA also may help increase levels of human growth hormone (HGH), which is said to help burn fat and provide more energy.
Since GABA is a relaxant, it can have mild sedating qualities and cause drowsiness. People may prefer to take it at bedtime.
Some GABA users have reported tickling, itchy or tingling sensations on the face and around the neck soon after taking GABA supplements. GABA is not associated with any allergic reactions, however.
Some people also have reported a quick and temporary effect on their breathing after taking GABA, which may involve rapid breathing or shortness of breath.
In some clinical studies, as noted by eMedTV, injected GABA has been linked to increased blood pressure and increased heart rate, as well as a generally unpleasant feeling.