Skin injury triggers food allergy in mouse model
- John Evans
- 33 minutes ago
- 3 min read
Findings from a new study suggest skin injuries may contribute to the development of food allergies. The study authors say this finding may help explain why the prevalence of childhood food allergy is higher in individuals with eczema.
The study, published in Science Immunology, was led by researchers at the Yale School of Medicine (YSM) in New Haven, Conn.
In a press release from the school, the authors note that for reasons scientists do not fully understand, chronic skin conditions such as eczema are linked to food allergies. The U.S. national prevalence of childhood food allergies is approximately 8%. However, that prevalence rises to 30% in children with eczema. Researchers have discovered that, in some cases, eczema can precede food allergies.
For this study, researchers worked with mice with different kinds of skin injuries, including lacerations and ultraviolet light damage. The investigators found that introducing new food proteins directly into the gut via a feeding tube at the time of skin damage induced new food allergies in the animals. The food had to be new to the animals; they wouldn’t develop allergies to foods they’d previously eaten. They also observed the introduction of the allergen had to happen within several hours of the skin injury. Foods introduced the next day seemed to be safe.
Before these findings, it was not clear whether events taking place so far apart from each other in the body could be linked through the immune system to trigger an allergy, the researchers said.
“It’s a mindset change that these things don’t have to happen in the same place in the body,” said the study’s lead author, Daniel Waizman, PhD, in the release. “We need to take a closer look at how these different organ systems talk to each other.”
Dr. Waizman is a former YSM doctoral student who is now a postdoctoral researcher at the University of California, San Francisco.
Some have speculated that allergens could enter the body through damaged and inflamed skin, leading to an allergy which can result in life-threatening anaphylaxis when food containing those allergens is later eaten.
The two senior authors of the study—Anna Eisenstein, MD, PhD, assistant professor of dermatology, and Andrew Wang, MD, PhD, associate professor of internal medicine (rheumatology)—did not find this hypothesis convincing. Both Wang and Eisenstein had young children who were relatively new to solid food around the time they initiated the study.
“Anna and I had chatted about this concept and agreed that, generally, our kids didn’t like to smear food on inflamed and damaged skin because it hurts,” Dr. Wang said. “So the three of us wondered if there were other ways that the immune system could ‘remember’ something you ate as being dangerous, a possibility which people may have overlooked.”
The existence of food allergies is somewhat of a scientific conundrum because the gut tends to be tolerant, immunologically speaking. The immune environment in our digestive tracts evolved so humans can safely eat a wide variety of foods and allow foreign but beneficial bacteria to take up residence in their digestive tracts. If food allergies are due to an immune reaction in a different organ, such as the skin, that could partially explain this conundrum.
The researchers tested several kinds of skin injuries, including puncture wounds and sunburns, at the same time as feeding mice the egg white protein ovalbumin through a feeding tube. Ovalbumin is a common food allergen. Even though different kinds of skin damage trigger different immune responses, all seemed to induce a food allergy to the egg white protein in mice that hadn’t previously been exposed to this protein. Environmental exposure through damaged skin was not required, as animals exposed to ovalbumin in their environments but not directly fed the protein did not develop an allergy.
The scientists identified several cytokines that were essential for the development of the egg white allergy. They hypothesize that some form of immune cell is responsible for coordinating signals between the skin and gut to trigger the allergy. They are currently working to pin down the identity of those go-between cells.
Although their findings may not have direct relevance for treating human food allergies, they do remind us not to ignore skin damage, the researchers said. Food allergies are not the only internal ailment tied to skin injuries; inflammatory bowel disease and rheumatoid arthritis have also been linked to eczema, and the skin condition psoriasis increases the risk of heart disease.
“As a dermatologist, to me, these findings really highlight the importance of treating inflammation on the skin,” said Dr. Eisenstein. “Treating skin disease is more than just treating what you see, but also the inflammation within and the potential for other systemic diseases.”
The research was supported by the U.S. National Institutes of Health (awards R01AI162645, R01AR080104, and K08AI17118202).