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Nailing the Patch Test: The Overlap Between Contact Dermatitis and Atopic Dermatitis

In this episode, Jonathan Silverberg, MD, reviews the overlap between atopic dermatitis and allergic contact dermatitis, and important considerations for utilizing patch testing among patients with AD, including managing flares. 

Dr Silverberg will present on this topic at the virtual Revolutionizing Atopic Dermatitis Conference, which will be held on December 13 and 14, 2020. For more information and to register, visit https://revolutionizingad.com.

For information about the George Washington School of Medicine Patch Testing Service, and to refer patients or schedule an appointment, please visit the GW website or call (202) 741‑2610.


Dr Silverberg is an associate professor of dermatology and director of the patch testing clinic at George Washington University School of Medicine and Health Sciences in Washington, DC.

Transcript

Hello. I’m Dr Jonathan Silverberg. I’m an Associate Professor of Dermatology and Director of the Patch Testing Clinic at George Washington University School of Medicine and Health Sciences.

Today I’ll be discussing the complex relationship and overlap of atopic dermatitis and allergic contact dermatitis and, specifically, how do we address special issues related to patch testing in atopic dermatitis patients.

I will also be presenting on this topic at the 2020 Revolutionizing Atopic Dermatitis Virtual Conference on December 13th and 14th, which is the first and only multidisciplinary conference dedicated to the treatment of atopic dermatitis and its comorbidities.

Other dermatology experts, including Amy Paller, Eric Simpson, Elaine Siegfried, Andrew Alexis, and Diamant Thaci will present on hot topics in atopic dermatitis, such as what to do if your patients fail a biologic, current and emerging therapies, and special considerations in skin of color.

There will also be speakers from allergy and immunology, sleep medicine, ophthalmology, psychology, and nursing to address the multidisciplinary aspects of atopic dermatitis care. Visit the website linked below at https://revolutionizingad.com for more information about the conference and to register.

There are several pathologic aspects of atopic dermatitis that predispose patients to potentially developing allergic reactions and contact dermatitis, as well as to irritant dermatitis.

First and foremost is the issue of barrier disruption that occurs in atopic dermatitis patients. We know that all patients, whether they have filaggrin genotype anomalies or not, all patients will have loss of filaggrin expression of the skin, loss of ceramide expression and other epidermal lipids, etc.

The dry skin phenotype that we know about with respect to dry skin, flaky skin in a broken‑down skin barrier. That broken‑down skin barrier is very important because the job of our skin is to keep the outside world out. That is true from an infection standpoint, but it’s also true from an allergen standpoint.

When the barrier is broken down, there is a greater potential for transcutaneous penetration of different potential allergens from the outside world. With that barrier disruption, patients are potentially going to have greater absorption, greater penetration of different ingredients that they’re getting exposed to from personal care products, potentially even from occupational exposures, etc.

In addition, there’s another risk factor, so to speak, for atopic dermatitis patients. That is simply exposure. Patients with atopic dermatitis are treating their skin with myriad skin products, personal care products, topical medications, emollients, moisturizers.

Most of these products come with a whole number of different ingredients, preservatives, surfactants, other penetration enhancers, etc. With that increased exposure, particularly repetitive exposure to some of these weaker allergens, patients are exposing themselves or increasing their risk of developing potential contact dermatitis.

It’s not only allergens that we have to worry about but irritants as well. Because with that broken‑down skin barrier and with that sensitive skin that happens in atopic dermatitis, patients are more vulnerable to exposures from outside irritants.

There are some fascinating studies that have shown atopic dermatitis patients have increased irritancy, increased sensitivity to irritant exposures, even between flares, when their skin disease is relatively quiescent.

There’s a number of other immunologic overlaps and other aspects of the disease as well, but those are really the key pathophysiologic concepts that underlie the relationship between atopic dermatitis and contact dermatitis.

There are several scenarios when contact dermatitis should be suspected in patients with atopic dermatitis. First, whenever we have a scenario of adolescent or adult‑onset atopic dermatitis, this is a little bit of a controversial entity. It does happen that patients will report adult‑onset, and in fact, it’s just atopic dermatitis with no evidence of contact dermatitis.

However, adult‑onset atopic dermatitis, in a sense, is a diagnosis of exclusion. First and foremost, we need to rule out the possibility of allergic contact dermatitis with patch testing. Other scenarios to think about would be when the lesional distribution is atypical for atopic dermatitis or one that is more localized and suggestive of a contact dermatitis.

For example, if there’s more of a predominance on the hands or feet or perhaps on the head and neck area or even maybe just the eyelids, certainly if we had patients without atopic dermatitis who presented this way, we would also be thinking about the possibility of contact dermatitis.

We need to be thinking about contact dermatitis even in the atopic patient because they can develop a superimposed allergic contact dermatitis that can really differentially affect those select locations or localized distributions.

Another scenario that we need to think about the possibility of contact dermatitis is when the dermatitis is recalcitrant to topical therapy or other conservative therapies. You look at their skin.

You think, “Well, this should really respond to a mid‑potency topical steroid and/or conservative therapy,” and it doesn’t. You definitely need to think about the possibility of contact dermatitis that is triggering the disease or perpetuating the disease.

Similarly, anytime you’re about to start a patient with atopic dermatitis on a systemic therapy or a biologic therapy, you should definitely consider patch testing because we hate the idea of putting patients on years‑long therapy when it might be as simple as, really, trigger avoidance.

Then finally, less common scenario that comes up but one you definitely need to pay attention to is when patients report that they use a topical steroid or other prescription topical therapy. It makes it better initially but then seems to quickly rebound or worsen it over time.

We definitely need to think about the possibility of an allergic contact dermatitis to a steroid or one of the excipients used in the prescription therapy. Those are some of the key considerations and scenarios that we think about in terms of patch testing in the atopic patient.

There are a number of therapies that can potentially impact the results of patch testing in general but certainly in the atopic dermatitis patient. First, systemic corticosteroids are definitely one of the most potent ones that can give us false negative reactions when it comes to patch testing.

The preferred approach is to have patients, if possible, completely wash out of systemic steroids, including intramuscular Kenalog, but the idea being they should wash out of that for a solid four weeks prior to patch testing. If that’s not possible, then even a three‑week washout would be considered by many to be OK.

Sometimes, that’s not even possible, in which case getting them down to a dose of somewhere equivalent of maybe 5 mg or 7.5 mg of a prednisone might not be unreasonable, but recognize that even in those scenarios, there can still be false negatives that emerge.

Other systemic immunosuppressants, like cyclosporine, methotrexate, azathioprine, mycophenolate, all have variable data in terms of how much they do or don’t suppress positive patch test reactions. Some guidelines have said it’s OK to patch test while on them.

My own personal experience is I have seen many scenarios of false negatives that have come up because of those agents. I would recommend trying to discontinue those completely and wash out for at least four weeks from those agents prior to patch testing.

Similarly, for phototherapy, a solid four‑week washout is advisable as well, particularly if they’re getting phototherapy on the back.

Topical therapies can really be washed out from the back per se or those areas where you’re applying the patches for approximately one to two weeks beforehand. You don’t need to have a full four‑week washout. One week is generally enough. If you want to err on the side of caution, you can say two weeks.

Then most recently would be now some of the biologics, like particularly dupilumab, published case reports, and others have as well, where patients have had positive reactions while being patch‑tested on dupilumab. On the other hand we’ve seen scenarios where patients had false negatives while on dupilumab.

It’s important to recognize if we can, it’s better to get these patients off of any of these kinds of confounding therapies while patch testing, but of course balancing that with the realistic or realism that it may not be possible. Because the minute you stop these therapies, the patient will flare up, and then they’re no longer a good candidate for patch testing either.

Dealing with flares between that window of stopping or tapering treatment and patch testing is not always easy to do. Ideally, you want the patient to be as clear as possible, ideally less than 10% body surface area of involved skin with atopic dermatitis, and you want the back leader.

I think those are important because in my experience, the patch test and really the data has shown that the patch test results become much less reliable when those two scenarios are not met.

If they flare up, the first thing you should try to do is try to optimize their topical therapy. Because if you can really clean things up with topical medications, then you only need a one‑week washout out of the topicals, not a full four‑week washout that you would with any of the systemics or potentially even longer with some of the biologic therapies that are out there.

Sometimes, if that’s not enough, then you may need to reinstitute therapy, cool off the skin, get them feeling better, and then try to taper them down to the lowest dose possible where their skin stays clear, but hopefully that the lower the dose, the less likely there will be the scenario of giving a false negative on patch testing.

It’s important to recognize though that if you’re going to patch test while patients are on some of these different therapies, systemic immunosuppressants, biologics, etc., that they should be counseled that there’s a possibility of a false negative and that if they ever do discontinue those medications successfully in the future, it may be worthwhile to revisit patch testing afterwards.

It’s not always easy to identify the patients who are allergic to their topical therapies that they’re using to treat the atopic dermatitis. Sometimes it’s easy.

Sometimes the patient will come in and say, “Every time I put on such and such moisturizer, my skin just doesn’t do well with it.” That’s obviously going to be a red flag and a clue that there might be something in there that the patient is allergic to or being irritated by.

Most of the time though, I think patients don’t know what exactly is their trigger. Otherwise, they wouldn’t be referred for patch testing in the first place. When that happens, we have to think fairly broadly.

One, you can have a scenario where a patient is allergic to their prescription topical therapy. The classic scenario described there is that the patient will report that the lesions get better short term, but then maybe 24 hours later, it seems to be getting worse, not better.

That could be a red flag that there’s something in that prescription agent that is setting it off. The same might be true for an over‑the‑counter therapy as well.

Often it’s the refractoriness of it in general, that the patient reports, “My topical therapies, they’re just not doing anything.” You’re confident that they are adherent to therapy, and nothing seems to be working.

That should also be a red flag that there might actually be something in their personal care product routine or their emollients, their over‑the‑counter therapies, their prescription therapies that may be ongoing trigger to their disease and perpetuating their disease. Sometimes, it’s maybe more of the fact that the most severe patients often have a contact allergen.

In those tougher cases, even when there isn’t a clear‑cut clue to contact dermatitis, you definitely want to make sure that you’re thinking about it and patch testing those patients because there may not be a clear‑cut history to support it, but in the end you find relevant allergens that can really be disease‑modifying with avoidance.

Patients with atopic dermatitis often feel desperate to get their itch and their lesions better. They will try almost anything to make it better. Many patients will use complementary and alternative therapies, all natural approaches. They’ll try just dozens of different over‑the‑counter personal care products, as emollients, as soothing agents, as topical anesthetics, you name it.

It’s important to recognize that patients are getting exposed to innumerable ingredients from these different exposures and from these different approaches to therapy. I think it’s important, when you’re talking to your atopic dermatitis patients and asking them about what they’re using, don’t just focus in on the prescription therapies.

Try to understand also what other complementary alternative approaches, over‑the‑counter approaches they may be using because from the lens of contact dermatitis, that is a particularly important issue, as they may be getting exposed to a variety of different botanical products, other sources.

I’ve had patients be allergic to some really interesting essential oils and natural products that they’re using as well. While these may have certain beneficial properties to the skin, if patients are allergic to them, it’s only going to cause them harm in the end.

It’s really important to address this with patients as well and to recognize, when you are patch testing, that expanded patch testing is indicated in the atopic dermatitis patient, in part to address all of these different types of allergen classes that they’re getting exposed to.

I think one of the most important takeaways for clinicians to really recognize is that in the textbooks, it’s often taught as if atopic dermatitis and contact dermatitis are these mutually exclusive disorders. It’s one or the other. It turns out that in the real world, it is far more complex.

There are patients who have a lifelong history of atopic dermatitis who develop allergic contact dermatitis later in life. You can have sort of independent courses of the two disorders.

Then there are scenarios where there are patients with atopic dermatitis who pick up contact allergies with time. Now the contact allergies fuel the underlying dermatitis and cause them to have a much more severe and refractory disease.

It’s important to recognize there’s a lot more complexity and overlap of these disorders than is often taught and to really pay attention to that complexity in clinical practice. Don’t just assume that if a patient walks in the door and has refractory dermatitis with a lifelong history of atopic derm, don’t just assume it’s purely atopic dermatitis.

Make sure you’re not missing a superimposed or overlapping allergic contact dermatitis.

Thank you very much for listening. If you have any questions or comments, please submit them in the feedback box below.

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