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The Role of Diet in AD: Q&A with Peter Lio, MD

LioIn atopic dermatitis (AD), the role of diet in disease progression and severity remains an elusive topic. At the 2019 American Academy of Dermatology, Peter Lio, MD, clinical assistant professor of dermatology and pediatrics at Northwestern University Feinberg School of Medicine in Chicago, IL, discussed the relationship between diet and AD. In an interview with The Dermatologist, Dr Lio spoke about the association between AD and food allergy, the efficacy of elimination diets, and how he discusses diet with patients and caregivers.

The Dermatologist: Could you elaborate on the relationship between food allergy and AD? Is the exclusion of certain foods possibly associated with a higher risk for the atopic march?

Dr Lio: Many families come in convinced that food is the “root cause” of eczema. The whole thing is very complex because—without a doubt—food allergies are associated with AD and perhaps as many as one-third of moderate to severe patients with AD have food allergies. 

True food allergies, such as hives, angioedema, and anaphylaxis, are very much associated with AD, and that correlation increases with disease severity. But, just as the association between fire trucks and fires does not mean that fire trucks cause fires, it seems that food allergies are not causing AD either, but are simply associated with it. Perhaps the most exciting development of the past few years takes this a step further, resulting in a delightful reversal as it is now thought that at least some food allergies (such as peanut) actually may be caused by AD! The thinking is that the impaired skin barrier allows food proteins to abnormally enter the body and thus stimulate allergy. This is exciting to me because it truly takes this story and turns it on its head. 

Remarkably, while just a few years ago the guidelines recommended delaying introduction of allergenic foods like peanuts into the diet, we now understand that this actually increases the risk of allergy by many fold. Instead, it bears out that early introduction is protective against at least certain types of food allergy. That said, we have much to learn on this and what type of ripple effects will come of these relatively drastic changes. 

Sometimes families want to avoid foods to just “try and see.” Historically, we might say that this is fine so long as overall nutrition is not impacted. However, a recent paper1 suggests that this may actually be a bad idea as avoiding certain foods increased the risk of actually developing anaphylaxis and other acute Immunoglobin E (IgE)-mediated reactions. So, there may be real harm in just avoiding foods to see what happens.

The Dermatologist: One study you include in your presentation, “Effective Therapy of Childhood Atopic Dermatitis Allays Food Allergy Concerns,” shows that 80% of foods thought to worsen AD do not.2 How has this affected the understanding of the relationship between food and AD, as well as AD and food allergies?

Dr Lio: It is incredibly difficult because, in the very limited time of a visit, sometimes the only thing a family wants to talk about is diet. Sadly, many of these families have already tried various dietary modifications—usually without success—but still want to know more about it. In the most severe cases, I have seen children with serious malnutrition from hyper-exclusive diets, like only taking rice milk. Tragically, the eczema tends to be as bad as ever, though I think the cognitive dissonance is so powerful that a common report is a hopeful “it was a little bit better.” 

 I think that studies like this one help us reassure the patient that they are not crazy and they are not alone. It really does seem like foods can drive AD, and certainly there are probably effects that are present. However, when we really lock things down, exclusion diets seem to be neither necessary nor sufficient for patients with AD and our time and energy are better spent elsewhere.

As we learn more about this connection, I find that I can now give a much more compelling narrative. It seems very important to heal the damaged skin, what I call the “leaky skin,” because it is possible that this is how food and other allergies are developing. The idea that if your house keeps getting broken into, one solution is to try to get rid of all the bad guys in the world. Another is to simply secure your house against bad guys, which is a lot more tenable.

The Dermatologist: Why do you think patients believe food is a contributing factor to AD severity?

Dr Lio: There are many customs, thoughts, and feelings around food. It is central to many things and the concept of food as medicine is compelling. I think for babies, in particular, there simply are not that many variables to consider, so it seems reasonable to pick on the one thing that they are doing—eating. Most importantly, it is something within our control.

The most frustrating part of AD is that it seems to have a mind of its own. Why me? Why now? Why here on the skin? An answer—any answer—feels better than just not knowing. Food is an easy target, and I am fearful to push too hard against food and look foolish. Certainly, some foods seem to be “inflammatory,” like dairy products in acne. It is not an allergy per se, but it does seem to drive inflammation.

Eating better certainly helps overall health, which can affect chronic inflammatory diseases. I do not want to seem too dismissive. But, in the short term, when folks are miserable, I do not think the option is to simply “cut out gluten and dairy” in someone without evidence of celiac disease or true IgE-mediated allergies to those foods. It is tantalizing, but not good medicine, I think.

The Dermatologist: What is the role of the microbiome in AD and should addressing microbiome diversity be a part of AD treatment, in your opinion?

Dr Lio: That is a longer discussion, and I presented another session on this topic. Yes, I think we are learning more that dysbiosis is a critical factor for at least a subpopulation of patients with AD and that there are probably a number of ways to help rebalance things from probiotics (topical and oral), to anti-bacterials, to simply improving the environment of the skin and gut. We have a lot to learn on this, but I think this is the next step. I do currently recommend probiotics for everyone with AD as I think there is probably a group that responds to them and I think the risk-benefit ratio is favorable. But we certainly still have a lot to learn!

The Dermatologist: How do you discuss dietary restrictions with patients and/or caregivers who believe food may be the cause of AD exacerbations? Do you also consider probiotic supplements for patients with AD?

Dr Lio: I often say that I wish diet modification did work. It would make things a lot easier. And, it is certainly possible that there are people for whom it works beautifully—and they never get to me because they are all clear. More power to them, I say. However, I wish they would quit blogging about it, because for the vast majority of patients I see, I am quite convinced that diet is not a major factor in driving their skin disease. We wrote a pretty comprehensive review3 last year and looked at many papers over many years, and I would say that this supports my clinical experience. 

That said, for adults, I do think it is fine to experiment with avoiding a certain food for a bit (with the caveat that this could actually increase the risk of actually developing a severe allergy to it) if there is a food they are convinced is making things worse. I also like to guide patients more generally on consuming a healthy diet: plant-based, cutting out processed foods as best they can, eliminating sugary foods, focusing on home-cooked fresh and whole foods. This is not always possible for some families, however. 

The Dermatologist: What recommendations or key take-aways do you want attendees to leave your presentation with?

Dr Lio: I think the key takeaways are:

  • Many patients will ask about diet and eczema: it is important to understand that they are deeply related but likely not in the way folks think.
  • For those with allergies verified by skin prick testing or serology, we of course recommend avoiding those foods strictly. A tough reality for those with AD is that such allergies are more common.
  • For those without allergies, it may actually be detrimental to avoid foods as they may be more likely to develop an allergy. 
  • Meanwhile, we should focus on healthy diet overall and intensify skin care as this may be the gateway to transcutaneous sensitization and developing more allergies if left unchecked.

The Dermatologist: Are there any other thoughts you would like to leave our readers?

Dr Lio: I have to remain humble with AD—there is still an awful lot we do not know. However, because there is real suffering, I think it is key to do the things that have the highest impact and are most reliable—excellent skin care, avoiding known allergens, appropriate topical medications, etc—as opposed to speculating on whether or not nightshades are making things slightly worse.

Also, I try to underline that a good diet is important for good health, and there is no doubt that eating well can help every organ system including the skin, so I do not want to dismiss the value of a healthy diet. At the same time, I want to focus our efforts on the key areas where we can rapidly make a difference. 

References:

1. Chang A, Robison R, Cai M, Singh AM. Natural history of food-triggered atopic dermatitis and

development of immediate reactions in children. J Allergy Clin Immunol Pract. 2016; 4(2):229–236.e1. doi:10.1016/j.jaip.2015.08.006.

2. Thompson MM, Hanifin JM. Effective therapy of childhood atopic dermatitis allays food allergy concerns. J Am Acad Dermatol. 2005; 53(2 suppl 2):S214-S219.

3. Lim NR, Lohman ME, Lio PA. The role of elimination diets in atopic dermatitis—a comprehensive review. Pediatr Dermatol. 2017;34(5):516-527. doi:10.1111/pde.13244.

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