Lactose intolerance is a digestive condition characterized by an inability to properly digest the milk sugar lactose. Those with lactose intolerance experience pain, bloating, gas and diarrhea within 30 minutes to two hours after consuming lactose. All types of lactose intolerance are a result of low levels of the enzyme lactase in the small intestine, although the cause of different types of lactose intolerance differs.
Primary
Primary lactose intolerance occurs as a result of the normal aging process. When you are a baby, your small intestine produces large amounts of lactase because milk is a major source of nutrition. In theory, the older you get, the less milk you need. Because of this, your small intestine naturally produces less lactase as you age. While this decline in lactase production does not affect some people, some people reach the point where they can no longer digest lactose. These people become lactose intolerant.
Secondary
Secondary lactose intolerance develops when the small intestine produces less lactase due to some type of illness or injury. Digestive diseases, like celiac disease, Crohn's disease and ulcerative colitis damage the lining of the small intestine. When the small intestine is damaged, it cannot produce adequate amounts of lactase. Physical injury to the small intestine or surgical removal of all or part of the small intestine may also lead to secondary lactose intolerance. If an underlying medical condition is the cause of lactose intolerance, medical treatment that controls the condition may help restore lactase levels and correct lactose intolerance, according to MayoClinic.com.
Congenital
Congenital, also called hereditary, lactose intolerance is the rarest form. Congenital lactose intolerance, which is characterized by an infant's inability to produce lactase, is present at birth. In order for a baby to be born with congenital lactose intolerance, both parents must pass down the defective gene, classifying the condition as autosomal recessive.
Considerations
It is important not to confuse lactose intolerance with a milk allergy. A milk allergy involves an abnormal immune response to one of the milk proteins -- whey or casein -- that results in hives, rash, swelling of the face, and in some cases, constriction of the throat. While lactose intolerance does not cause any serious damage or complications to the body, a milk allergy can be life threatening for those who are severely allergic to one of the milk proteins. If you experience any of the symptoms of an allergy after consuming milk, call a doctor immediately. If you have trouble breathing or swallowing, go to the emergency room.
