There are a number of sites that claim that massaging a point in the webbing between thumb and index finger can relieve headaches.
One pressure point that may help relieve your headaches is located in the webbing of your hand between your thumb and index finger. Hold your hand so your palm is facing the floor and pinch the webbing with the thumb and forefinger of your opposite hand. Squeeze this area until it is tender and continue to massage for 15 to 30 seconds. Repeat on the opposite hand. Do not stimulate this point if you are pregnant.
The page provides a seemingly credible reference site titled "University of Maryland Medicine" which 404s.
The “Hoku point” (LI4) is excellent for headache relief. It is located on the back of the hand, in the webbing where the thumb and index finger meet. Find the exact point by bringing your thumb and index finger together. The muscle will bulge a little--that's the spot.
Squeeze the point by putting your thumb on the point, and your index finger on the palm side of your hand. Angle the pressure toward the bone that connects with the index finger. Hold for one minute and switch hands.
Do not use the Hoku Point if you are pregnant.
Press the top of the feet, in the web between the big and second toes. You can either use your hands for this, working both feet at the same time, or you can use the heel of the opposite foot to work one foot at a time. Once again, hold for a minute or until you feel relief. This point is Lv3.
Most of these suggestions of acupressure for headaches are taken from Acupressure’s Potent Points, by Michael Reed Gach.
In the webbing between the thumb and your index finger is a pressure point well known to cure headaches. The point is located close to the bone in that area, not in the center of the webbing. Use your thumb and index finger to squeeze the point on your opposite hand. If you are doing it properly, you will feel the nerve beneath the skin and some pressure as you squeeze. Squeeze the point for a minute on each hand. Be sure to take deep breaths while treating yourself.
Use your feet. According to the art of reflexology, points on the feet are connected to the body's organs. By stimulating certain points on the feet, you can relieve a headache. In the space between the big toe and second toe is a pressure point. Use your thumb to apply pressure to the top of this spot. Rub the area for one minute.
Considering how frequently people experience headaches and the seemingly rudimentary techniques suggested above, have there been any scientific studies conducted on this subject? Also, why shouldn't pregnant women massage the webbing between the thumb and forefingers, or their big and second toes?