NEW YORK (Reuters Health) - A new case series from Australia links goat-milk allergy to previous use of skincare products containing goat milk.
"We undertook some studies that showed that the allergic antibodies (Immunoglobulin E or IgE), that cause the allergic reactions to goat's milk in the blood of the patients, also bound to the goat's milk proteins contained in skincare soap and lotion," Dr. Jo Douglass of Royal Melbourne Hospital told Reuters Health by email.
"These laboratory studies strengthen the link between the development of severe food allergy to goat and sheep milks in our patients and the skincare products," she said, "suggesting that the skincare products are responsible for the allergy."
In a research letter in the journal Clinical & Experimental Allergy, Dr. Douglass and her colleagues describe clinical features and lab findings from seven patients with goat-milk allergy. The patients were selected via a retrospective audit of all cases at Royal Melbourne Hospital's Pathology Department between 2016 and 2019 for which the measurement of goat and/or sheep milk specific immunoglobulin E (sIgE) reached at least 0.35 kUA/L.
Following a review of the patients' medical records, they were invited to submit to additional skin testing and blood work, as well as control evaluations for allergic responses to cow milk and rye grass pollen.
All seven had used goat milk soap topically in recent years. Six had atopic dermatitis, one of several conditions toward which goat's milk-based skin products are marketed as more sensitive.
The patients had developed a serious IgE-mediated allergy to orally ingested goat-milk products, with most presenting symptoms such as anaphylaxis, throat tightness, rashes, urticaria and dyspnea
Skin-prick testing was conducted for reactions to commercial goat milk extract, sourced from pharmaceutical company ALK-Abello. Prick-prick testing was conducted for sheep-milk yogurt, camel milk, buffalo-milk mozzarella and cow milk, but was not performed for fresh goat milk for safety reasons. The patients' blood serum was tested for sIgE to cow, goat and sheep milk, cow-milk casein and beta-lactoglobulin (BLG) using the ImmunoCAP platform.
The skin-prick tests were positive for all seven patients with respect to goat-milk extract and sheep-milk yogurt. Four patients also had positive skin-prick tests for one or more of the other milk products.
These results were echoed in the specific IgE findings, where all patients tested sIgE positive to goat milk, ranging from 4.79 to 37.1 kUA/L, as well as sheep milk, ranging from 0.83 to more than 100 kUA/L. Three patients had measurable cow-milk sIgE greater than 0.1 kUA/L, correlated with the presence of casein sIgE, but the researchers found only one of these cases to be a clinical cow-milk allergy.
Further competitive IgE binding immunoblot studies suggested that the goat-milk skincare products led to both allergic skin sensitivity and oral ingestion allergies to goat milk. The competitive tests showed a significant reduction in IgE binding to goat milk cheese when patient serum had been pre-incubated with goat-milk soap or lotion. The researchers say this suggests sIgE in patients' serum is binding to a shared epitope present in all three products.
"I believe this is a very important study, a reliable study," Dr. Aristo Vojdani, a clinical professor of preventive medicine at Loma Linda University in California, told Reuters Health by phone. "The methodologies are very solid."
Dr. Vojdani, who has studied immune reactivity to mammalian and plant-based milks, but was not involved in the new work, said the findings were in line with a growing body of evidence on how allergic sensitization can develop via topical exposures. He expressed hope that further research might lead regulators to pay more attention to the issue.
"I never thought there would be some milk - goat or cow's milk or any other product like that - in cosmetics," Dr. Vojdani said. "They should at least put it on the label and put something saying that, if you are allergic to milk, you should not use this product. Saying it's 'natural' doesn't mean anything."
Dr. Douglass noted that while her group's study "was small and only looked at those who suffered very severe allergy," it would be important to determine how often consumers of goat-milk-based skincare products develop an allergic sensitization to goat or sheep milk.
"Such a study could also provide more precise evidence of the safety or risk of using these products," she said.
SOURCE: https://bit.ly/3KTfQHW Clinical & Experimental Allergy, online April 6, 2022.
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