Thursday, November 15, 2012

Contact dermatitis, delayed allergies, and eczema

Contact dermatitis is a more important and complex factor than I thought for patients with atopic dermatitis, I learned from reading a presentation given by Dr. Luz Fonacier at the annual meeting of the American College of Allergy, Asthma and Immunology, held this year in Anaheim, CA. (I was not present at the meeting.)

Fonacier is head of the allergy section of the Division of Rheumatology, Allergy & Immunology at Winthrop University Hospital in Mineola, NY. Her talk, titled “Food Allergy and Atopic Dermatitis: Generating a Common Approach with the Dermatologist,” covered many well-known techniques to diagnose food allergy. She also devoted a large section to a controversial test: the atopy patch test.

What stood out for me was the role of contact dermatitis in atopic dermatitis. According to Fonacier, contact dermatitis, a specific type of allergic reaction to substances such as certain metals and fragrances, affects roughly two-thirds of young (infant to teenage) patients with chronic eczema. Rash and inflammation from contact dermatitis can intensify AD and change the long-term course of the disease, presumably for the worse--by exposing you to more allergens and pathogens.

While contact dermatitis often affects the hands, arms, and face, a systemic exposure to an allergen to which a person has a contact allergy can affect skin over the entire body. Metals, fragrances, and other substances that cause contact dermatitis are often present in foods. When a person eats a food containing a substance to which he or she has a contact allergy, it can manifest as a body-wide skin inflammation.

So how is this different from “classic” food allergy?

The differences lie in the timing and pathway of the reaction. “Type I” allergens such as wheat, soy, milk, and the usual culprits provoke a specific type of allergy, initiated by IgE-class antibodies, that appears over 30 minutes to two hours.

“Type IV” allergens—and I am not even sure I am using the correct term for these substances—cause a “delayed-type hypersensitivity” reaction driven by T cells that manifests hours or days later.

Nickel. You probably don't want to eat this stuff.
But it's in your cutlery and tofu.
Fonacier lists several allergens in food that can cause systemic contact dermatitis: the most common are nickel sulfate and something called “balsam of Peru,” a natural resin that contains a mixture of oils and chemicals and is used in many processed products.

Nickel is overwhelmingly found in soy and a small number of other foods, according to Fonacier’s slides. (That means that you can have a type IV allergy to soy but not necessarily test positive on a skin prick test or IgE assay.) Balsam of Peru, in contrast, is found in a wide variety of foods. Check out slide 15 of the presentation—see spices, citrus, tomatoes? I have no idea how balsam of Peru ends up in citrus peel or tomatoes; maybe it's an agriculture or food industry thing [update: Fonacier says that tomatoes contain chemicals similar to those in balsam of Peru].

Now, how to diagnose contact dermatitis? Patch testing, in which a nurse applies an array of patches containing potential allergens to a patient’s back. About two days later, an allergist looks for inflamed spots, and the corresponding patches indicate which items you should avoid.

Balsam of Peru. Appearing soon in toothpaste near you.
(And spices, and citrus, and tomatoes, and fragrances...)
Fonacier does explain patch testing in her slides, probably because it’s so obvious to an allergist. Instead, she devotes a large section of the presentation to the “atopy patch test,” or APT, which is a patch test in which the allergens are dairy, wheat, soy, and so on--those commonly assessed for type I allergies by skin prick tests and specific IgE measurements. But an APT tests for type IV hypersensitivity reactions, the delayed ones.

The advantages of the APT are that it apparently can predict type IV allergies to cow’s milk, egg, and wheat pretty well. The disadvantages are that it takes a long time and the person observing the results has to be well-trained. According to one slide, an NIAID expert panel recommends that the APT not be routinely used in the clinic because it is not as reliable as oral food challenges.

So when does Fonacier recommend using the APT? If a patient has a history of severe and persistent AD, and skin prick and IgE tests have been done, and no trigger has been identified—or if there are multiple instances of IgE reactions that have no apparent connection to AD—then it's time to try the APT.

4 comments:

  1. Thanks for your post. I am a long term eczema sufferer, and have had the allergy tests you refer to in your post. They take place during a 5 day span. My results revealed several substances that I showed a reaction to, one of which was Balsam of Peru.

    Let me add that these tests were performed at the allergy department of Duke university Medical Center. After researching each of the substances that showed a reaction, I too discovered the cross-over of Balsam of Peru and the many foods that contain this substance. Many like lemons, cinnamon, etc. I use on a daily basis as I cook a lot. So I decided to write to my physician to ask if I should avoid these since I tested positive and her response absolutely astounded me.

    She said that after consulting with a colleague, they concluded that there was probably no reason to avoid these foods as they weren't contributing to my eczema. Needless to say that I did not return for anymore follow up visits. It's scary to think I am more attuned to what I am dealing with than they are---if it's not something they've studied, then it's not within their realm of thinking.

    Turns out I am allergic to fragrance, stabilizers, preservatives, basically all the ingredients in shampoos, conditioners, styling products, toothpaste, moisturizers, makeup. As a woman, this really sucks, but has greatly reduced my expenses since I can now only use baby products for sensitive skin. Coconut oil has become my new moisturizer after trying every other natural oil on the market. The results have been remarkable so I will continue this therapy indefinitely.

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  2. Thank you for your story! Allergies and food reactions are so complicated. I feel like you're a bit harsh on your former doctor--but I understand. Glad you found a solution that works for you.

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  3. I have a skin problem I don't really know the cause of my problem but thanks to your information. I like to follow what you are using in there. I hope it works in me too.
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  4. Ironically, I have had atopic dermatitis and the only skin cream that helped my horrible eye peeling and cracking contained Balsam of Peru! I wouldn't say she is being harsh with her doctor since the problem she had was long standing. It is scary to think we know more than MD's about our conditions but as an autoimmune sufferer, I find that is the case. We learn more from support groups because you then have a larger team, a larger group that may have your specific set of symptoms.

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