Differentiating between lactose intolerance and dairy allergies can be difficult, since they have some of the same symptoms. However, lactose intolerance and dairy allergies follow different courses, often appearing at different ages and can differ in their symptoms. Lactose intolerance is not as likely to cause a rash as a dairy allergy is, and does not cause the same types of rash. Lactose intolerance is also more common than dairy allergies, affecting around 30 percent of people in the United States, the Women's Health Resource reports.
Causes
The causes of dairy allergy and lactose intolerance are quite different. Lactose intolerance develops because a person lacks an enzyme called lactase, or produces less lactase than other people. The tendency toward low lactase levels is often inherited, with blacks, Asians, Native Americans and Hispanics more likely to develop the problem than Caucasians. Dairy allergy, on the other hand, is an allergic reaction caused by a hyper-immune response to certain proteins. Allergies can also run in families.
Timing
Dairy allergies can appear in infants. Of the approximately 2 percent of children with true milk allergies, many will improve by age 2 or 3, according to pediatrician and author William Sears, M.D. Lactose intolerance normally doesn't develop until after age 2, since small children produce more lactase enzymes than older children and adults. Premature infants may develop lactose intolerance because their immature intestines don't produce lactase. People with lactose intolerance do not outgrow the condition, which often worsens with age.
Symptoms
Both dairy allergy and lactose intolerance can cause gastrointestinal upsets such as diarrhea, vomiting, stomach pain or cramping, gas and bloating. Lactose intolerant children may develop a reddened area around the anus, the opening of the rectum. Dairy allergy may also cause skin reactions such as rash, including diaper rash, hives, eczema, facial swelling, especially around the eyes and mouth or tightening in throat. Itching of the skin or throat can also occur in dairy allergy but not in lactose intolerance.
Significance
While lactose intolerance can be uncomfortable and inconvenient, dairy allergy can be life threatening. Hives, skin welts that can develop inside the throat, can make breathing difficult. The throat can swell completely closed, making air exchange impossible. People with severe dairy allergies should carry an epinephrine injection to treat a life-threatening allergic reaction. People with lactose intolerance do not experience this type of reaction and do not need to carry an epinephrine injection or special identification. If they take lactase enzymes or dairy products containing added enzymes, they can often consume some milk products.
