What environmental pollutants are the greatest threat to skin health? For Stephanie Pascale, a family nurse practitioner specializing in dermatology, the answer might be your shampoo or lip gloss.

“Contact dermatitis is a rash—an allergic reaction—that develops when you come into contact with something that irritates your skin,” Ms. Pascale explains. “And such allergies and sensitivities have been on the rise, because we’re exposed to so many more irritants—often out of our awareness.

“It’s estimated, for example, that people use between six and twelve personal care products every day—over 90 percent of them containing one or more chemicals or allergens linked to contact dermatitis.

Health&Healing: What are the most common sources of contact dermatitis?

MS. PASCALE: Fragrances, preservatives, dyes, and metals. And, right now, two irritants that I’m seeing most often are propolis and nickel. Propolis—which is a beeswax—is in a ton of oral products, such as lipstick. And nickel—which is most often found in jewelry—is actually in many other products, including some foods. So, it can sometimes be tricky to identify.

Those are among the many allergens that cause contact dermatitis. The problem is that they—especially fragrances—can be found in such a wide variety of the products that we use regularly. The most common ones are personal care products (shampoo, cosmetics, soap, even sunscreens), and household products (cleaning products, laundry detergents, dryer sheets, air fresheners). But it can be any irritant that comes in contact with the skin. 

Dyes, in clothing and even in tattoos, are a problem; and—surprisingly—we see skin reactions to implants, such as those in a knee replacement. Medicines can also trigger an allergic reaction. For example, hydrochlorothiazide—a common blood pressure medicine and diuretic—can be a problem, as can some statins.

And it’s important to point out that an indirect—and frequent—cause of contact dermatitis is misinformation. One of the challenges of living in the age of the Internet and social media is that there is so much information, which is often contradictory and can be inaccurate. And we’re often persuaded to use personal care products that can be problematic. Because what works well for one person may be poison for another. Even products marketed as “natural” or “hypoallergenic” frequently contain irritants. In fact, studies have shown that over 75 percent of them do.

A good example are lavender, rosemary, and tea tree oil—ingredients promoted in many self-care products And these are three very potent and very common allergens. It’s important to remember that just because it’s “natural” doesn’t mean it’s good for you.

H&H: How do you identify the sources of contact allergies?

MS. PASCALE: Although we often can quickly identify likely culprits, it can also be challenging. So I always start with a lot of questions: What kind of products are you using? Are you wearing a perfume? Have you switched your deodorant? Have you switched your lingerie?

Obvious cues are products with fragrances, dyes, and metals, and things that are alcohol based. The location of the rash is also an important clue: is it where clothing or jewelry is in contact? That might suggest a problem with dyes or laundry products or with nickel. And often the way the rash presents can point to the allergen. Reaction to shampoos, for example might not show up as irritation on the scalp, but as rashes on the neck and shoulders—the rinse off pattern.

And, while a new product might be the culprit, it’s also possible that a product you’ve used for years may finally cause a reaction, sometimes because the manufacturer has changed the chemistry in some way. That’s the frustrating part of dermatology: sometimes you can be using a product you assume is safe because you’ve been using it for so long but it’s actually the culprit.

H&H: How do you treat contact dermatitis?

MS. PASCALE: The most important treatment, of course, is avoidance. And that depends on accurately identifying the culprit. In the meantime, we need to provide relief for the patient’s rash.

So diagnosis and treatment are part of the same process. We’ll have the patient engage in steps to isolate and identify the toxin(s), such as changing to neutral, unscented laundry or skin care products. At the same time, we’ll apply topical steroids or non-steroidal medications to reduce the flare or stop it altogether.

In some cases, we may need to do patch testing to isolate an allergen, but that’s a cumbersome and expensive process, so we typically work with patients to isolate the allergen even as we treat the rash. This may take a few weeks, but is normally an effective approach.

But, you don’t want someone on topical steroids long-term. So, with persistent problems where the allergen is hard to identify, we might do some patch testing or consider something like Dupixent, which decreases your body’s sensitivity to the things it comes in contact with without suppressing the immune system. And sometimes you can even do both at the same time.

In those cases, we can often decrease the inflammation enough to where we can slowly reintroduce products in order to identify the source.