High and Low

• When air pressure is high, the air pressure in an area is higher than the pressure in the air that surrounds it. High barometric pressure usually means that good weather is in the works and there will be clear skies and cool temperatures. When the pressure is low, storms, rain and warmer weather are on the way.
  
  

Joint Pain

• When barometric pressure is high people who are arthritic are apt to experience less joint pain than when the atmospheric pressure is low. High barometric pressure and low humidity are the best weather conditions for someone who suffers from joint pain, according to the Journal of Rheumatology. Robert Jamison of the Brigham and Women's Hospital's Pain Management Center undertook studies regarding weather and physical changes and pain in the human body. He concluded that changes in barometric pressure do cause pain. High pressure decreases joint pain and low pressure increases pain.
  
  

Weather-Sensitivity

• Changes in air pressure affect oxygen levels, particularly for those people who are weather-sensitive. Some people experience headaches that may be caused by barometric pressure. Some researchers theorize that blood vessels in the head contract or expand to compensate for the change in air pressure. When the blood vessels change size, it affects the flow of blood and can result in a headache. When air pressure goes up or down it can also cause ear pain and sinus flare-ups.
  
  

Allergies

• When air pressure is low and the humidity is high, wet mold releases spores. When the pressure goes up and the humidity is low, dry molds release their spores, which can cause allergic reactions in humans.