Goat’s milk skin product usage may lead to ‘severe’ goat’s milk allergy

A small cohort of patients who used goat’s milk-containing treatments for inflammatory skin conditions subsequently developed severe goat’s milk allergy, according to a research letter published in Clinical & Experimental Allergy.

This case series adds to the research suggesting that application of food-based skin care products to inflamed skin can lead to the development of new food allergies, according to Joseph Francis De Luca, a PhD candidate in the department of medicine at University of Melbourne in Australia, and colleagues.

Researchers noted growing numbers of patients using topical goat’s milk products to manage inflammatory dermatopathies and then developing systemic reactions to goat’s milk or cheese ingestion.

Theorizing that this sensitization began due to the topical exposure to goat products, the researchers conducted a retrospective audit of all specific IgE results for goat’s and/or sheep’s milk tallied by the Royal Melbourne Hospital pathology department between 2016 and 2019. They identified seven patients who experienced symptoms consistent with IgE-mediated reactions to ingested goat’s or sheep’s milk or cheese products had used topical goat’s milk products to manage inflammatory conditions before their allergy emerged. Six of these patients had atopic dermatitis, and five had allergic rhinitis.

Patients received skin prick testing to commercial goat’s milk extract and prick-prick testing to sheep’s milk yogurt, camel’s milk, buffalo’s milk mozzarella and cow’s milk. SPTs were positive for goat’s milk extract and sheep’s milk yogurt in all seven patients. Three patients only had positive tests for goat’s and sheep’s milk. Four additionally were positive for buffalo mozzarella, cow’s milk or camel’s milk.

Also, researchers tested patients for serum sIgE to cow’s, goat’s and sheep’s milk, cow’s milk casein and beta lactoglobulin. Results showed sIgE tests all were positive for goat’s milk, ranging from 4.79 kUA/L to 37.1 kUA/L, and for sheep’s milk, ranging from 0.83 kUA/L to more than 100 kUA/L.

However, patients with allergy to goat’s milk showed little cross-reactivity to cow’s milk, the researchers wrote, despite that most patients with primary cow’s milk allergy usually also react to goat’s milk.

The researchers then established competition studies to test for commonality between IgE for goat cheese proteins and goat’s milk soap. They used commercially available soaps that included goat’s milk and control soaps to preincubate patient sera before exposing blots to cheese proteins.

These studies demonstrated significant reductions in IgE binding to products that included goat’s milk cheese when the patient serum was preincubated with goat’s milk soap or lotion, suggesting the sIgE in the serum binds a shared epitope in all three products, the researchers wrote.

Overall, the results suggested that sensitization to goat’s milk occurred via epicutaneous exposure.

“This case series of seven adults provides evidence for a relationship between the use of goat’s milk-containing treatments for inflammatory skin conditions and subsequent development of new-onset severe goat’s milk allergy,” the researchers wrote.

“It could be postulated that this association is confounded by a higher incidence of new-onset food allergy in atopic individuals. However, our immunoblotting studies

demonstrate cross-reactivity of patient IgE to goat’s milk and goat’s milk-derived skincare products, implying a causal association.”

The researchers expressed concern about the extensive marketing of skin products that use goat’s milk to patients with “sensitive skin” who often have underlying inflammatory skin conditions, adding that these findings have implications for the regulation of the skin care industry.