Medically reviewed on June 16, 2022 by Jordan Stachel, M.S., RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.
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For many people, food intolerance and food allergy are synonymous. In the case of dairy allergies and lactose intolerance, they are commonly conflated. But they involve two wholly different systems of the body—and, often, two entirely different segments of the population.
Dairy allergies are classified as an immune disorder, while lactose intolerance expressly pertains to the digestive system. Moreover, most dairy allergies primarily appear in infancy, but lactose intolerance commonly occurs in adulthood.
Marked differences aside, the two disorders are triggered by the same ingredient: milk. Knowing the unique traits of each condition and how to discover whether you may be affected is a critical first step in making empowered decisions about your diet and health.
A dairy allergy, or a milk allergy, is an immune disorder triggered when an individual ingests milk products. It’s commonly triggered by cow’s milk, but sheep’s milk, goat’s milk, and other animal-derived milk can also lead to symptoms .
Dairy allergies primarily appear within the first 6 months of life . When a dairy allergy is not mediated by immunoglobulin (IgE), one of the immune system’s primary antibodies, symptoms may take days or weeks to manifest. Gradual onset symptoms could include:
In more severe cases, specifically when IgE is involved in the immune response triggered by dairy, symptoms may set in within minutes . Rapid onset symptoms may include :
Rapid-onset dairy allergies are considered serious due to their potential to trigger anaphylactic shock .
During anaphylaxis, breathing passages constrict, making respiration extremely difficult, which triggers a significant lowering of blood pressure . Because anaphylaxis requires immediate emergency treatment to avoid potentially fatal outcomes, identifying a dairy allergy early is critical for avoiding trigger ingredients and ensuring young children’s well-being.
Like all food allergies, dairy allergies primarily pertain to the immune system. Lactose intolerance, in contrast, chiefly involves the digestive system.
When people with a dairy allergy ingest milk or milk products, their immune system reacts to two key proteins found in milk :
This causes their immune system to flood the body with histamines, a chemical responsible for the inflammatory reactions underlying sufferers’ allergic symptoms .
While the mechanisms behind dairy allergies are well understood, the root cause of their occurrence is not known. Researchers believe approximately 4.9% of children younger than 3 years old present with a cow’s milk allergy, though there appears to be a lower incidence with infants who are breastfed [2,3].
Fortunately, most babies and young children with dairy allergies outgrow their condition by adolescence . Testing can be an essential component of dairy allergy diagnosis and treatment, enabling parents and loved ones to identify whether or not the disorder has receded with time.
Lactose intolerance, or lactose malabsorption, refers to a condition in which an individual cannot digest lactose, a type of sugar constituent in dairy products, without experiencing digestive distress .
Lactose intolerance symptoms typically set in between 30 minutes and 2 hours after an individual has ingested foods containing milk . Consuming milk or milk-based products can cause :
While uncomfortable, lactose intolerance is not considered a serious medical condition and can usually be managed with dietary and lifestyle adjustments .
Even so, living with lactose intolerance can interfere with an individuals’ ability to meet their daily vitamin D and calcium quotas. For this reason, it’s critical to identify whether you have the condition to ensure you meet your nutritional needs.
Lactose intolerance occurs when an individual lacks sufficient reserves of lactase, an enzyme responsible for processing lactose that is produced by the small intestine .
When lactase enzyme production falls short, lactose advances to the colon without being broken down into the simple sugars known as glucose and galactose. This causes bacteria to feed on unprocessed lactose, resulting in a string of uncomfortable digestive symptoms .
Not all forms of lactose intolerance occur in the same circumstances. Healthcare providers recognize 3 main types of lactose intolerance:
One common misconception about lactose malabsorption is that it’s an exception rather than a norm. However, from a global perspective, as much as 68% of the world’s population cannot digest milk without some degree of digestive discomfort .
For people with a lactase deficiency, it can be frustrating to give up dairy-rich treats like delicious cheeses and summertime ice cream sundaes. Fortunately, testing for dairy sensitivity or a dairy allergy is a crucial first step in determining how to adapt gracefully to a diet that cares for your body’s unique needs.
It’s not uncommon for people to confuse dairy allergies and lactose intolerance, but there are five crucial distinctions to be made between them:
Comparing your systems and knowing your likelihood of being affected by dairy allergies or lactose intolerance is the first step in determining whether you have either condition. The second is to undergo testing.
Healthcare providers use three types of tests to confirm the existence of a dairy allergy :
Like any other food allergy, the single most important factor in dairy allergy treatment is to eliminate foods that trigger an allergic response.
That said, immune thresholds may differ from individual to individual. For instance, some people with a dairy allergy experience no symptoms after consuming fermented milk products (e.g., yogurt) or milk that has been exposed to high heat (e.g., bakery items) .
Most importantly, young children and adults who exhibit severe allergic reactions to milk must carry epinephrine to limit their likelihood of experiencing anaphylaxis if exposed to dairy. Keeping epinephrine dispensers (e.g., EpiPens) on hand—and knowing how to use them—is paramount for protecting against the worst outcomes of a dairy allergy.
There are two commonly used testing approaches used to confirm lactose intolerance :
Triggers for lactose intolerance can be highly variable between individuals. In some cases, small amounts of dairy are tolerated well, or symptoms may heal by carefully introducing your digestive system to lactose-containing products .
For this reason, food sensitivity tests can be an important, comprehensive step in identifying unique triggers. The better you know which foods do (and don’t) sit well with your stomach, the more consciously—and confidently—you can design a diet that fits your life and tastes.
If you’re wondering whether milk products may be triggering symptoms, Everlywell can help you make informed decisions about what foods to enjoy and which to limit. The Everlywell at-home Food Allergy Test measures your body’s immunoglobulin E (IgE) reactivity to common food allergens, including cow's milk.
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