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Cosmetic conundrums

Contact dermatitis experts discuss key cosmetic allergens and how to investigate which product may be causing a patient’s allergic reaction.


By Emily Margosian, Assistant Editor, September 1, 2023

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Thousands of substances can cause an allergic skin reaction, offering a broad lineup of potential “suspects” for contact dermatitis patients and their dermatologists. As consumer skin care and cosmetic markets continue to expand, new products — and allergens — may pose additional challenges. According to a recent JAAD study, contact dermatitis from personal care products is increasing, affecting 28.8% of males and 39.5% of females.

“As our understanding of contact allergens changes over time, cosmeceutical companies evolve their ingredients to match current trends. For example, in recent years, formaldehyde-based preservatives have become less common in products due to reports of high rates of contact dermatitis and public demand for ‘clean’ beauty,” said JiaDe (Jeff) Yu, MD, FAAD, director of Occupational and Contact Dermatitis and assistant professor of dermatology at Massachusetts General and Harvard Medical School, and president-elect of American Contact Dermatitis Society. “However, phasing out these preservatives has led to the advent of new, potentially more allergenic ingredients, such as methylisothiazolinone, which has skyrocketed from a little-known preservative to the second-most common contact allergen over the last 10 years.”

This month, contact dermatitis experts discuss “hot” allergens found in personal care products, and share their tips for how physicians and patients can work together to identify and manage allergic cosmetic reactions.

Short on time?

Key takeaways from this article:

  • “Hot” emerging allergens found in personal care products include alkyl glucosides, preservatives methylisothiazolinone (MI) and methylchloroisothiazolinone (MCI), lanolin, and fragrance compounds linalool and limonene.

  • Patients can utilize resources such as the Contact Allergen Management Program (CAMP) database for lists of safe products according to their specific allergens.

  • While history-taking is an important part of the investigative process, patch testing is almost always needed to positively identify which allergen and product(s) are the culprit.

  • Additional patch testing panels are often required to identify a cosmetic allergy.

  • Management of cosmetic-induced ACD includes ceasing use of the product, and topical steroids if the rash persists.

  • If ACD is suspected, dermatologists should not hesitate to refer a patient for extended patch testing if they do not have adequate patch testing resources at their practice.

Common allergens

Allergens commonly found in cosmetic or manufactured products typically fall into five broad classes:

  • Natural rubber

  • Fragrances

  • Preservatives

  • Dyes

  • Metals (nickel and gold)

The FDA has compiled a list of ingredients found in cosmetic products that are more likely to cause allergic reactions, organized by class. However, among this list, contact dermatitis experts have isolated key allergens of note, causing increased rates of sensitization within American markets.

Hot allergens

Alkyl glucosides

Named the 2017 Allergen of Year, alkyl glucosides are surfactants found in many personal care products to help produce lather, including shampoo, conditioner, and shower gel. “This allergy has become more common because products containing alkyl glucosides are often marketed as being ‘eco-friendly’ or ‘natural’ because they come from plants and are biodegradable,” explained William D. James, MD, FAAD, Paul R. Gross professor of dermatology and director of education at Perelman School of Medicine at the University of Pennsylvania. “What sets it apart is the marketing aspect.”

Due to its use as a surfactant in many bathing products, individuals with alkyl glucoside allergy typically present with a “rinse-off” pattern of dermatitis around the hairline, ears, or down the sides of the neck. “This is one of the allergens that we’re seeing more, especially in men. Men in general are buying more in the way of personal care products than they were in the past, and studies have indicated an increase in facial reactions observed in men due to cosmetic use,” said Dr. James.

Methylisothiazolinone (MI) and Methylchloroisothiazolinone (MCI)

MI and MCI are preservatives that can be found separately in consumer products or as a mix (MCI/MI). These preservatives are used in personal care products like shampoos and soaps but are also found in more obscure sources like residential wall paints, some nail cosmetics, and school glues. “Anything that has water in it needs a preservative, and preservatives are historically something that we see causing problems with contact dermatitis,” said Dr. James.

“When you’re looking at hot allergens, the biggest ones are probably MI and MCI,” agreed Christen Mowad, MD, FAAD, director of the Contact and Occupational Dermatitis Clinic at Geisinger Medical Center. “Over the years, MI has really increased in prevalence and significance, and was named the Allergen of the Year in 2013 because it was so common. It’s also a relatively new allergen, and often the most relevant to a patient’s personal care products. However, it’s not on the FDA-approved screening series, so it can be missed if not tested for alone because it doesn’t always get picked up if you only test to the mix (MCI/MI).”

While the popularity of MI and MCI as commercial preservatives has waxed and waned over time, they have a long history as prominent sensitizers.

“The history of MI is very interesting, because it was an epidemic many years ago,” said Jonathan Hale Zippin, MD, PhD, FAAD, vice chair of research, director of Contact, Occupational, and Photodermatitis Unit, and associate attending dermatologist and associate professor of dermatology at Weill Medical College of Cornell. “During the ‘parabens scare’, when parabens were considered to be carcinogenic, industry started pulling them out of products. The problem is, there are only so many preservatives that work well, and MI was brought back into the mix. Subsequently, we’ve started seeing a huge uptick in sensitization again to that allergen.”

“We’re currently seeing a big rise in MI allergy,” agreed Dr. James. “MCI/MI used to be a very prevalent preservative allergen 10 or 15 years ago. We knew MCI was a much more potent sensitizer than MI, and we work a lot with industry to keep them abreast of which ingredients are causing problems. They decided to take the MCI out and use MI by itself because it was less allergenic. However, it was also a less-effective preservative, so they upped the concentration of MI. Now, I think it’s the second-most common sensitizer in the United States.”


Named this year’s Allergen of the Year, lanolin is a sometimes-overlooked emollient derived from the oil glands of sheep and used in many consumer products. “Because lanolin has been perceived as a ‘weak’ allergen, it is used in many over-the-counter products including cosmetics and moisturizers. Nipple creams tout it as a ‘safe’ alternative to petroleum jelly,” explained Blair A. Jenkins, MD, PhD, in a June 2023 DermWorld column discussing her recent Dermatitis paper on lanolin.

According to Dr. James, while lanolin allergy is not a new topic of discussion, the ingredient’s continued inclusion in a wide range of consumer products makes it an important cosmetic allergen for consideration. “It’s almost exclusively found in personal care products or cosmetics, and there’s currently a big market for moisturizers. As such, over the past 10 years or so, lanolin has become a much more commonly found allergen that we patch test to.”

Linalool and limonene

Many people have a sensitivity to fragrance. However, some scents present more of a problem than others. According to contact dermatitis experts, hydroperoxides linalool and limonene oxide have recently emerged as increasingly prevalent fragrance allergens.

“Linalool is usually associated with more of a floral fragrance, like lavender. Whereas when you hear the name ‘limonene,’ you might think it sounds like it comes from citrus plants — and indeed it does. It gives a citrus kind of a smell,” said Dr. James. “They’re among the top fragrance sensitizers. The problem with these is often products will just list ‘fragrance,’ as opposed to the individual fragrance chemical, which makes it harder for patients to manage.”

“The toughest allergy to manage is probably fragrance, because of the way it’s listed on product labels,” agreed Dr. Mowad. “However, when you go to someone who specializes in patch testing, they can provide you with narratives that include where it’s found, what it’s called, how to avoid it, and what products you can use in place of it. There are databases available that also provide patients with safe lists. The one that I most frequently use is the Contact Allergen Management Program (CAMP) database, which is managed by the American Contact Dermatitis Society.”

2023 Allergen of the year: Lanolin

DermWorld physician editor Kathryn Schwarzenberger, MD, FAAD, talks with Blair A. Jenkins, MD, PhD, about how a “golden oldie” was named allergen of the year, and why dermatologists should be thinking about lanolin allergies today. Read more.

Is it allergic contact dermatitis?

According to experts, there are some key indications that a patient may be suffering from allergic contact dermatitis (ACD) due to a cosmetic product they’re using.

“Any time somebody develops a chronic, consistent rash that’s localized to a very specific area and seems to sort of wax and wane over time, it’s almost always a contact dermatitis,” said Dr. Zippin. “It could be irritant or allergic, which is where patch testing comes in, but generally we don’t develop localized rashes in a specific area unless there’s an external trigger.”

Commonly affected areas include the face, specifically on the eyelids, lips, neck, or scalp, as well as the hands and feet. “Hand dermatitis is something we see frequently that has us thinking about potential occupational disease. For example, people doing wet work or cosmetic work. We also see a fair number of health care workers who have contact dermatitis on their hands,” said Dr. James. “Facial dermatitis and isolated eyelid dermatitis from things like mascara or eye drops are also something we think about regarding cosmetic ACD. We see the same thing on the lips. There’s a substance in many balms called propolis that can cause an allergic reaction around the mouth. So, there are definite patterns that dermatologists dealing with contact dermatitis recognize.”

ACD is also often a delayed reaction, making it difficult to connect to a particular product encounter. “For example, if you’re allergic to your deodorant, the rash would not appear immediately as you’d expect other allergies, like those to food or things found in the environment,” explained Dr. Yu. “This is because contact dermatitis is mediated by your T cells, not histamine-containing mast cells. Therefore, it can take 24-72 hours for reactions to develop, making direct association hard.”

“ACD is difficult to identify by taking a history alone,” agreed Dr. James. “If you’re allergic to cats; you start to sneeze if you walk into a room with one — that’s an immediate allergy. It’s what allergists look for when they do prick testing, and it’s different than what we’re looking for. For example, if someone’s eyelids are red and itchy, they think, ‘What did I put on my eyes this morning?’ However, it may be something they put on yesterday, or the day before. Even if you do highly suspect a particular product, there are multiple ingredients, and you don’t know which of those is the culprit. The patient can buy a different brand, but that brand may have the same allergen that was in the other product, and that’s where things can get confusing.”

Investigate and identify: How to find the culprit

While contact dermatitis experts agree patch testing is the gold standard of contact allergen detection, the process of identifying which cosmetic exposure may be causing a reaction often involves additional investigative work between patient and physician.

“It’s like detective work; it’s quite fun,” said Dr. Mowad. “You ask them about all the things they’re putting on their skin: things that are new and old things that they use periodically. I also ask patients about their job and what kind of hobbies they have. Are they doing crafts? Do they take care of people? Are they using products on another person that might be causing the dermatitis? For example, children, elderly people, or pets? Those questions don’t necessarily help you identify the chemical or the specific ingredient, but they help you look at certain classes to consider when patch testing.”

“Each question begets additional questions,” agreed Dr. Zippin. “In broad strokes, I’m trying to determine what exposures they have on a daily basis. Staple questions for women include how they do their nails, or whether they dye their hair. Same thing for men, I have a variety of questions that go into what their exposures are. Sometimes I’ll see situations where men will develop a rash on their face, and it turns out it’s due to a hair product their wife is using that’s getting on their pillow. That’s why I always ask about who patients live with, and what their exposures are as well.”

Following an initial consult, patch testing is almost always required to precisely pinpoint the source of an allergic reaction, even if a patient has a strong suspicion about a particular product. “There’s really no way to confirm without patch testing,” said Dr. Yu. “Many times, patients will have certain products they suspect they are allergic to. However, this is seldom accurate, as the patient does not always remember if they came in contact with another possible contact allergen.”

Patch testing is also critical to determining whether multiple products may be causing a patient’s ACD, versus just one. “Once we know what they’re sensitive to, we can go back to their products and interrogate the ingredients. Sometimes people come with clear stories where they say, ‘I introduced one product, and now I have a rash.’ Well, that product may indeed contain the ingredient they are allergic to, but it could also be found in multiple products they’re using perhaps at low levels,” explained Dr. Zippin. “Once they add a new product, the increased exposure to a given ingredient rises above a certain threshold for them, and now they’re getting a rash. So even when we can identify a culprit product, without patch testing, it’s hard to provide comprehensive guidance for all exposures to avoid going forward.”

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Patch testing pearls

Among the most-used patch tests are the Thin-Layer Rapid Use Epicutaneous Test (T.R.U.E. Test), American Contact Dermatitis Society (ACDS) Core Allergen Series, and North American Contact Dermatitis Group (NACDG) Standard Series. However, according to experts, allergens included in these tests do not change frequently, and often supplemental panels are required to adequately evaluate patients.

“The more extensive the patch testing the better,” recommended Dr. Yu. “For a suspected cosmetic allergen, most patch testing experts will use at least 80 to 90 allergens as part of the ‘core’ series and then add on additional allergens such as the cosmetic panel, hairdressing panel, nail cosmetic panel, or fragrance panel, depending on the suspected source. Often, patients might go home with 150+ allergens on their back!”

“In my opinion, the minimum number of allergens you should be testing anyone to is generally around 115 to 120 allergens,” added Dr. Zippin. “The North American Contact Dermatitis Group series is pretty good, but it usually misses a few things. I have a supplemental series I’ve generated, and then I have all these other panels that depend on the patient’s history.”

According to Dr. Mowad, the patient history collected during an initial consult is key to determining which additional series to test for beyond the expanded trays. “If they’re a florist, you’re going to patch test to floral allergens. If they’re a nail technician, you’re going to patch test different types of acrylates. Certainly vocation, job history, and hobbies are going to help direct what allergens to test beyond the expanded tray. For a suspected fragrance allergy, for example, there is Fragrance Mix I, which has eight chemicals in it, and because that was not able to keep up with the fragrance industry and all the new allergens being introduced, we now have Fragrance Mix II, which has six additional allergens to help detect those allergic to fragrance. We continue to see new fragrance allergens and need to test for them as well, such as linalool and limonene.”

Best practices for management

The best way to get rid of a reaction to a cosmetic product? Stop using it.

“If you’re patch tested and determined to have a specific allergen, then it’s important to avoid that in any shape or form. That’s why those narratives we can provide, and the CAMP databases are so helpful, so they know where else to avoid it and what is safe to use,” said Dr. Mowad. “In the acute stage, we usually treat with a topical steroid of varying potencies, depending on where the rash is. If you can get them to truly avoid the allergen, the rash usually goes away. Not always, but usually.”

“Treatment with topical medications such as topical steroids, calcineurin inhibitors, or small molecules like crisaborole or ruxolitinib are most effective,” said Dr. Yu. “For extensive reactions, an oral steroid may be necessary.”

According to Dr. Zippin, contextualizing a patient’s allergy within their daily life is key to eliminating future exposures — and subsequent flare ups. “My goal with the consultation is to gain a very clear picture as to what their exposures are, so that when we get the positives at the end of the testing, I can go into the room with a clear idea as to how these allergens are relevant for them,” he explained. “What should never be done is to just hand them a list of five or six allergens, and say, ‘You’re positive to these. Avoid them!’ It’s critically important to put the allergens in context to the types of products they’re using or may be encountering.”

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When to refer for patch testing

Not all dermatologists patch test. However, contact dermatitis experts recommend that any patient with a suspected case of ACD be referred to a physician who does.

“If it’s something you think a patient might have, they should be patch tested. If the person evaluating them doesn’t have the capacity to do that, then they should certainly seek out a colleague who does,” said Dr. Mowad. “You can find dermatologists who perform patch testing at www.contactderm.org/find.”

“For other dermatologists, the biggest thing I would say is that it’s important to test broadly. Unfortunately, I see a lot of ‘half-testing’ that goes on, and that can lead to problems with insurance,” said Dr. Zippin. “I’m of the belief that if you really feel your patient has allergic contact dermatitis, and you’re seeing a lot of those patients, incorporate patch testing into your practice and get all the allergens. It is a lot of expense, time, and training for staff. So, if you cannot do this in your practice — and I can appreciate why a physician may not be able to — then I highly recommend that you pair up with somebody who does comprehensive patch testing and send those patients out for patch testing.”