From the Guidelines
Diagnosing a dairy allergy requires a comprehensive approach that includes a detailed medical history, physical examination, and specific testing methods, with the most recent and highest quality study suggesting that a combination of skin prick testing, blood tests measuring specific IgE antibodies, and oral food challenges under medical supervision is the most reliable method for diagnosis 1.
Key Considerations
- A detailed clinical history is essential to identify symptoms that occur after dairy consumption, such as hives, wheezing, vomiting, or digestive issues.
- Skin prick testing is often the first diagnostic test, where small amounts of milk protein are placed on the skin to observe for allergic reactions.
- Blood tests measuring specific IgE antibodies to milk proteins (casein, whey) can quantify the allergic response.
- For definitive diagnosis, an oral food challenge may be conducted under medical supervision, where increasing amounts of dairy are consumed while monitoring for reactions.
Testing Methods
- Skin prick testing (SPT) is an in vivo test that assesses for immediate/type I hypersensitivity reactions.
- Serum specific IgE level determination is an in vitro assay that measures food-specific IgE levels.
- Oral food challenges, such as double-blind, placebo-controlled oral food challenges (DBPCFC), are considered the gold standard for diagnosing food allergy.
Important Notes
- A positive test result alone is not sufficient to diagnose a dairy allergy, and clinical correlation and confirmation are necessary to establish the presence of allergic disease.
- The negative predictive value of SPT and specific IgE measurement is high (>95%), while the specificity and positive predictive value are low (40 to 60%).
- Higher specific IgE levels and larger wheal sizes (>8–10 mm) are associated with a greater likelihood of reaction on challenge.
Management and Treatment
- Accurate diagnosis is essential for proper management, as dairy allergies can range from mild to life-threatening and require appropriate avoidance strategies.
- Comprehensive counseling regarding food allergy includes food avoidance, nutritional monitoring, label reading, recognition of signs and symptoms of anaphylaxis, and use of epinephrine autoinjector devices.
From the Research
Diagnosis of Dairy Allergy
The diagnosis of dairy allergy involves a combination of medical history, physical examination, and diagnostic tests.
- The diagnostic approach includes performing a medical history, physical examination, diagnostic elimination diets, skin prick tests, specific IgE measurements, and oral food challenges 2.
- Clinical response to elimination diet followed by a positive oral food challenge is diagnostic for cow's milk protein allergy 3.
- Food allergies are broadly classified into immunoglobulin E (IgE)-mediated, non-IgE-mediated, or mixed food allergic reactions, and the diagnosis can be complicated due to the distinct clinical and immunologic features of each type 4.
Diagnostic Tests
- Skin prick test and specific IgE measurements can be used to diagnose IgE-mediated dairy allergy 5, 6.
- However, for non-IgE-mediated dairy allergy, skin prick test and specific IgE levels are not useful in diagnosis, and alternative tests such as sigmoidoscopy and rectal biopsy may be considered 3.
- Oral food challenges can be used to confirm the diagnosis of dairy allergy 2, 3.
Management and Prevention
- Strict avoidance of the offending allergen is the only therapeutic option for dairy allergy 2, 3.
- Exclusive breastfeeding for at least 4 months and up to 6 months is desirable for primary prevention of allergy 2.
- Infants with a documented hereditary risk of allergy who cannot be breastfed exclusively should receive a formula with confirmed reduced allergenicity, such as a partially or extensively hydrolyzed formula, to prevent allergic reactions 2.