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Michael Pappas, a well-known creative perfumer, once needed to make a holiday scent. “I went into our attic, pulled out some holiday things, and I got emotional with all the memories,” he recalls. Realizing that a Christmas tree is the centerpiece of the holidays for many people, one of the first scents that came to mind was Frasier fir pine, something that sparks holiday feelings for many people and evokes emotions and memories.
“Fragrances trigger a memory of an experience in your brain and evoke an emotion in your heart,” Pappas explains. But creating a pine scent is not as easy as you might think, and it creates challenges. A perfect pine aroma might include many separate ingredients, some with the potential to cause a dermal allergy.
For companies to responsibly use scents, they need to test each one rigorously. But, they first need to understand how skin allergies work.
What’s an allergen?
Allergies are widespread and commonly misunderstood. David Basketter, a toxicologist, explains there are multiple kinds of allergies. Basketter worked for nearly three decades at Unilever’s UK-based safety and environmental assurance center and has since been an independent toxicologist for more than 10 years. Here, he helps us focus on dermal allergies to fragrances.
What is a skin allergy? It is “an immune mechanism,” Basketter says, so it takes some time — and enough exposure — to develop. The immune system must learn to react to the allergen, which is a process called induction (See ‘Anatomy of an Allergy.’). After the immune system is primed to an allergen, sufficient further exposure triggers an allergic reaction. This second process is called elicitation. In a dermal allergy to a fragrance, elicitation creates a rash or red bumps on the skin.
It might appear that some people get allergies and some don’t, but that’s not really the case. Take poison ivy, for example. “Everybody — and I mean everybody — is susceptible to this kind of allergy,” Basketter explains. “Everybody can be sensitized to poison ivy, and the same is true for a number of other reasonably common skin allergens.” Despite that, only some people suffer from allergic reactions. Part of this — maybe a lot of it — depends on the degree of exposure. More exposure increases the likelihood of becoming sensitized to a particular allergen. As Basketter explains, “The more exposure you have, the more likely you are to become sensitized.” In other words, it’s like a dose-response curve: More exposure, or dose, increases the odds of a reaction, or response.
There is much variability in responses to different allergens between people. “Some people are just very resistant to an allergen and some people are sensitive,” Basketter points out. Additionally, someone might be super-sensitive to one allergen and resistant to others.
Many people believe you can outgrow an allergy. You can’t. If you become sensitized to an allergen and are then not exposed to it for decades, your sensitivity could fade slowly over time. “The problem is that, because you are allergic, one or two exposures boosts you back up, kind of like a vaccination booster, and you’re back where you started,” Basketter says.
So, if you were susceptible to a rash from poison ivy as a child, but haven’t had it in years, don’t roll in a field of it — at least, don’t do it twice. You’ll probably regret it!
What are your odds?
If someone tested a random group of people, only 20% would react to some kind of skin allergen, according to Basketter. To see if someone has been sensitized to an allergen, or a group of them, clinicians use a diagnostic patch test, which exposes a person to 30–40 substances that most frequently cause skin allergies. A patient wears the patch for 48 hours, and a skin reaction to a particular allergen can indicate sensitization. “Then, little red blobs will pop up on skin and persist for a week or two,” Basketter explains.
Fragrance sensitivities arise far less frequently. “You would probably find that about 1 to 2% of the people in a random group will react to one or another fragrance allergen,” Basketter says. In a test of a random group for a reaction to a specific fragrance chemical, the metric would generally fall to 0.1% or lower.
For those who do react to fragrances, the result is far from the serious reaction of, say, a peanut allergy. “With fragrance skin allergies, they don’t lead to anaphylaxis,” Basketter explains. A fragrance allergy may trigger a skin rash that can usually be resolved with a low-dose hydrocortisone cream. People with stronger reactions can see a dermatologist for prescription treatments, such as more potent steroids.
“For a smaller proportion of people, they can become even more sensitive, and they get airborne contact dermatitis,” Basketter says. “This is not respiratory, but the fragrance in the air that comes in contact with the skin leads to a dermal reaction. That’s rare, but it does happen.”
What protections exist?
Until 20 years ago, fragrances were largely ignored as potential allergens. Then, in 1996 in the UK, Basketter and Ian White, a consultant dermatologist at Guy’s Hospital in London, organized a symposium to “highlight problems of there being perhaps too much fragrance allergy, and to try to get the fragrance industry to deal with it,” Basketter recalls.
Eventually, some organizations decided this problem needed to be addressed. In March 2005, the European Union (EU) added an amendment to the EU Cosmetics Regulation that required 26 fragrance allergens to be listed on labels when used in cosmetics or household products.
For cosmetics that customers leave on, for example, any of the 26 allergens in concentrations of 10 parts per million must be listed; for products that get rinsed off, these allergens must be listed when they exceed 100 parts per million.
Beyond the EU 26, many consumers are reassured by claims of “natural" ingredients. But when a scientist looks inside anything — natural or not — it’s all chemistry (See ‘Chemistry is Everywhere,’ page 12.). When it comes to fragrances, some companies suggest that natural oils cause no problems, but these, too, can cause skin allergies, and they are not usually identified. “Where the fragrance-supply industry can control certain aspects of the fragrances it uses, it can’t really control essential oils in the same way,” Basketter explains. For one thing, allergenic compounds in natural oils may not be on the EU list of 26.
Plus, some common natural elements can readily cause skin reactions. In one study of 2,320 people, 1.8% of them experienced allergic reactions to tea tree oil.
That figure matches the overall reaction of a random group of people to fragrance
allergens as a group. So, when it comes to natural oils, says Basketter. “It’s extremely hard, actually, for sensitized individuals to avoid them.” Instead, the best protection is providing clear information for the consumer.
Scientific solution
In May 2016, SC Johnson put together a team of experts, from fragrance creators to toxicologists, to examine the current scientific studies of fragrance allergens.
The team pored over about 3,000 datasets from academic and industrial studies and analyzed the results for potential skin allergens that appear on lists from many sources, including national regulatory and fragrance industry lists.
The expert panel also considered inputs from the European Scientific Committee on Consumer Safety, as well as data from dermatology clinics and supplier safety data sheets. SC Johnson is working to put the findings to use and, by 2018, will start adding information about skin allergens to www.WhatsInsideSCJohnson.com, with the aim of listing all the potential skin allergens in every product.
The transparency embraced by SC Johnson could trigger changes across the industry. As Basketter says about the fragrance industry. “It has recognized that there are people out there criticizing them, but the industry can learn from that and address the concerns, which is the right thing to do.”
This article was created for SC Johnson by Scientific American Custom Media, a division separate from the magazine’s board of editors.
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