A Patch Test Can Reveal If You're Allergic to Your Beauty Products

This year, I spent one of the hottest weeks of the New York City summer unable to shower. For two of those days, my back was almost completely covered in surgical sticky tape that was reinforcing large adhesive patches loaded with allergens specifically chosen to make my skin itch violently. What's even more perverse was that was that for the rest of that week, I was praying fervently for them to bestow me with itchy flare-ups. Welcome to skin patch-testing.

As a person with sensitive skin, my face reacts dramatically to most newly-introduced skin-care and several hair-care products. My skin gets red and itchy until it forms raised welts or a grainy rash, both of which can take weeks to subside. I use mostly fragrance-free skin care to avoid scent-related irritants, but that's still not a foolproof solution, and I get flare-ups more times than I'd like.

So, desperate to figure out which ingredients my skin is actually reacting to, I visited Hudson Dermatology and Laser Surgery in New York City to see Tamara Lazic Strugar MD, a board-certified dermatologist who specializes in diagnosing skin allergies through skin patch-testing, the most thorough way to uncover allergies both mundane and debilitating.

Meet the experts:

  • Tamara Lazic Strugar, MD, a New York City-based board-certified dermatologist based in New York City.
  • Lindsey Bordone, MD, a board-certified dermatologist and director of medical dermatology at Columbia University Medical Center in New York City.

What exactly are skin allergens?

"A skin allergen is a chemical that touches your skin, making your immune system think it is under attack, so it overreacts and produces antibodies to fight the allergen, resulting in a red, typically itchy rash called contact dermatitis," says Dr. Lazic Strugar. Common examples of allergens are poison ivy or nickel found in costume jewelry. Personal-care and skin-care products also contain allergens such as fragrances and preservatives, which commonly cause reactions called contact dermatitis.

There are two types of contact dermatitis: irritant and allergic. Irritant Contact Dermatitis (ICD) is a skin irritation that occurs minutes or hours after contact with a substance like harsh cleaning products, causing burning, stinging, or pain. Allergic Contact Dermatitis (ACD) on the other hand, is a rash caused by an allergic reaction to a chemical that touches your skin. It takes days after contact with an allergen for the rash to develop, so pinpointing the source can be challenging.

Skin allergies can lead to a wide array of problems, says Lindsey Bordone, MD, a board-certified dermatologist and director of medical dermatology at Columbia University Medical Center in New York City. "The most significant challenge I hear patients report is sleep disturbance. If they are very itchy they are unable to sleep or wake up scratching. This begins to affect their work performance and overall happiness," she says.

So, what is skin patch testing?

A patch test assesses an individual's skin reaction to a variety of substances they might encounter in their daily lives, and is performed by applying purified allergens to the skin to see which — if any — cause an allergic reaction.

"Patch testing is the gold standard and only accurate way of diagnosing allergic contact dermatitis and identifying the allergen [causing it]," says Dr. Lazic Strugar. It can be performed by a dermatologist or an allergist, who will apply pre-made patches loaded with individual allergens in a grid on the body. The patches are stuck onto a patient's clean, unbroken skin, typically on the back, and are left in place for 48 hours, allowing the allergens to be in constant contact with the skin. The patches are then removed, and the back is marked with a Sharpie to keep track of where the patches were placed. A more basic patch test (known as the True Test) assesses sensitivity to around 40 allergens, but Lazic Strugar deems this a shortcut, and advises opting for the more intensive version that tests for 90 or more allergens.

The skin is analyzed around 72 or 96 hours after patch placement to check for any positive reactions. The back must stay dry during that entire period, which means no bathing or showering (sponge baths that don't wet the back are allowed). Since the patches need to closely adhere to the skin, exercise is also discouraged.

As for my own patch test, it was a minor irritation to have a back full of patches for days: they made me super hot and I couldn’t shower, so on a blazing week, that was a bit agonizing. I managed well with sponge baths, though I missed the feeling of standing in a cold shower at the end of a hot day. But I was determined to find my allergen(s), so I powered through it. Doing this in any other season but high summer should be a pretty painless process.

Who's a good candidate for patch testing?

"Typically, when we see a patient with worsening rashes, without a significant history of eczema, we start to think about environmental triggers that could be causing their rashes," explains Dr. Bordone. Dermatologists will also keenly observe the location of the rash before deciding to test, and how long redness or burning begins after using a product, whether that's minutes hours, or days. Recurrent, itchy bumps, or rashes on the face or hands get the most positive patch test results.

But if the reaction is occurring on both hands and feet, Dr. Lazic Strugar might not recommend testing, and her diagnosis may lean more towards eczema or psoriasis, which are more systemic, symmetric, and often involve palms and soles. "If it's ACD, it's very unlikely those allergens are touching your hands and feet only but not the rest of the body," says Dr. Lazic Strugar.

Another example of placement being important: if the scalp is itchy and the rash is on the side of the face and the neck, that's usually from shampoo or conditioner, while a rash on the side of the face or front of the neck could often be from perfumes, and testing a patient with a rash in these locations could prove worthwhile.

All that said, Dr. Lazic Strugar also believes that pretty much everybody who has been suffering from eczema should also have a patch test. It may turn out your eczema symptoms aren't due to eczema at all.

"Eczema is an umbrella term that dermatologists diagnose all the time for itchy rashes, which include contact dermatitis. If it's itchy, flaky and we don't know where it's coming from, it's eczema," she explains. "A skin biopsy won't tell you where it's coming from, so I recommend everyone with eczema get tested because it's an easy answer. If you find out you're allergic to a fragrance, remove it and you never have to live with that rash again." She also notes that even a diagnosis of atopic dermatitis, which is usually genetic, warrants it.

"Those patients are actually more prone to develop skin allergies, and the allergy might be the trigger behind their flare-ups," she says. If the allergic triggers are removed, they can still have flare-ups from stress or other triggers, but the incidence will be greatly lowered.

What happens after a patch test?

After the cause of your reactions have been identified, dermatologists that specialize in patch testing provide the patient with the name of the ingredients they're allergic to as well as any aliases that various manufacturers use, so they know what products to avoid. Patch testing and subsequent allergen avoidance can potentially provide a cure rather than having to manage a long-term skin condition with medicated cream and a prayer.

After my own 96 hours were up post-appointment, I went in for my reading. Sadly for me, I reacted to none of the 90 allergens, and Dr. Lazic Strugar deemed it more likely to be irritant contact dermatitis. "Almost 80 percent of cases of dermatitis are irritant not allergic. For you, that means your skin is sensitive, and will get irritated by certain things which won't necessarily show up on the patch test," she explains. Dr. Lazic Strugar also observed that it was only my face that showed the symptoms and not the rest of my body, making it less likely to be an allergic reaction. "True allergy will show up wherever the allergen touches your body," she adds.

My test gave Dr. Lazic Strugar a more straight-forward path for my diagnosis, but she often encounters cases where some high-level detective work is warranted to figure out where a patient might be encountering their allergen so it can be removed from their day-to-day. For example, one patient's patch test returned a strong positive for ethylenediamine, a more uncommon chemical. She quizzed the patient about her work and hobbies, and found out she was a yoga instructor. The ingredients listed on her high-end yoga mat didn't contain ethylenediamine, but Dr. Lazic Strugar contacted the company anyway for a full ingredient list, and finally got lucky: ethylenediamine was one of the unlisted ingredients.

"She was routinely rubbing into the mat while sweaty, so the allergen absorbs quickly," she explains. Other such mystery cases were caused by the sulfites in beer, and for one baker, her severe hand eczema came from daily contact with kneading dough laced with Balsam of Peru, a substance found in ingredients like cinnamon.

Dr. Bordone recently saw a patient with red, swollen eyelids who had swapped all her products with new brands, stopped wearing eye makeup, and pared down her routine to just concealer, but was still reacting. "It turned out it was the rubber in her makeup sponges. She lived with this for over a year before she came in for patch testing and we identified the rubber allergy," says Dr. Bordone.

What are the most common allergens in beauty products?

Fragrance and preservative ingredients are common triggers in beauty and personal-care products. Methylisothiazolinone, commonly called MI, tops the list, according to Dr. Bordone, along with Paraphenylenediamine (PPD), which is widely used in permanent hair dyes that frequently causes severe allergies. "They can appear all over the body and people don't often make the connection with their hair dye, because they think that will only manifest on the scalp. However, you can get severe eyelid swelling and a rash all over the body," says Dr. Lazic Strugar.

Fragrances, both synthetic and natural that include essential oils, can be allergy-inducing. Linalool and limonene are two citrus-derived fragrance compounds that are common culprits. "If patients get skin-care products from Whole Foods and it's organic, they think it's not causing their rash, but essential oils are actually very sensitizing," Dr. Lazic Strugar says.

Allergies to these ingredients aren't always instant. In fact, people sometimes notice that they develop allergies to a product after months or even years, and struggle to believe they're now allergic to it after using it reliably for so long. That's because of a phenomenon called cumulative exposure, which is usually how ACD develops. "It never happens the first time you touch something. Your body needs to see it at least twice to get sensitized to it and then produce this memory immune response every time it sees that chemical," says Dr. Lazic Strugar.

A very common example of that is the notorious Neosporin allergy. Neosporin, a topical antibiotic, has become a product that some dermatologists have condemned. "Neomycin, the main active ingredient, is very highly sensitizing. It's commonly used and people tend to overuse it, slathering it on cracked, dry skin, or chapped lips. In those cases, when you're using it on an already compromised skin barrier, it's more likely to cause an allergic reaction," she says. But before you begin to suspect all your beauty products of irritating your skin, check in with your dermatologist or allergist to see if a patch test is right for you.