Going upside down in a yoga practice will help give you a new perspective, but it is not meant to make your world spin. If your handstand is creating dizziness or a light-headed feeling, a subtle aspect of your posture is missing. Engaging a technique called Root Lock will balance your posture and your view.
All yoga postures stimulate at least one of the five "winds" of your body. Inversions, such as the handstand -- called "Adho Mukha Vrkasana" -- stimulate the "wind" known as "Apana Vayu" -- the force responsible for moving things down and out. According to yoga practitioners, this force regulates the processes of elimination. Since handstands have a very strong energetic impact, you may feel Apanay Vayu very deeply. This may be why you feel light-headed after doing yoga inversion poses.
To balance Apana Vayu, yogis engage a technique called "Mula Bundha" -- "Bundha" means lock or seal and "Mula" is translated as root, foundation or beginning. In this case, the root is the foundation at the base of your pelvis -- the perineum. Engaging the muscles here will keep Apana Vayu from descending too quickly, thus balancing your posture.
To properly engage Root Lock sit in a comfortable position with your spine straight. Relax your body and breathe in full, deep, equal breaths. Bring your awareness to the perineum. Hold your attention there as you breathe in and out. Staying relaxed, inhale and gently engage the muscles of your pelvic floor -- your front, side and back. Exhale and release the contraction. Practice for 25 breaths. As you improve, move to the second stage by keeping your muscles engaged on both the inhale and the exhale.
Mula Bundha takes time to cultivate; be patient as you build the muscles of the perineum area, just as you would for any other practice.
Inversions are contraindicated for people with high blood pressure, heart conditions, neck injuries, epilepsy and eye conditions such as a detached retina as well as for people with depression.