Perfume allergy: Why do some people develop an itchy rash? What’s the safest way to test a new scent?

Given our perpetual hot, humid and sweaty state, the use of deodorants and perfumes should be a legal requirement. Compared to what the French did in the 15th century, when they literally sprayed everything, including guests, clothing, furniture, walls and even dinnerware with perfume, we must smell like hobos. Extravagant, yes, but bet they smelled better than us, even though they didn’t bathe as often as we do.
If you’re crying foul about having to use perfume or cologne, you’ll have a solid case if you have a perfume allergy that affects 1 per cent of adults worldwide (for children and adolescents, it’s 1.8 per cent).
“Two types of itchy rash can occur following direct contact with a perfume or fragrance,” said Adjunct Associate Professor Leow Yung Hian. “The patient can present with irritant contact dermatitis arising from irritation, meaning that the product is either too strong or too concentrated. Anyone can develop irritant contact dermatitis if the product is present at the ‘wrong’ concentration.” 
He continued: “The other skin reaction is an allergic contact dermatitis, whereby the patient is allergic to the specific fragrance per se, meaning that repeat exposure to the same fragrance has the potential of inducing an even more severe itchy rash that may progress to a generalised rash”.
At National Skin Centre, where Adj Assoc Prof Leow is a senior consultant, he has seen patients with itchy rashes following the use of fragranced products, “not just perfumes or colognes per se”.  “As fragrance is ubiquitous, it is difficult to verify,” he said.
Dr Christopher Foo, a specialist in dermatology and a consultant with Raffles Skin & Aesthetics, said that he sees about one case of allergic contact dermatitis every few months. “I suspect that the reason could be because most reactions are mild. Therefore, patients visit a general practitioner instead.”
No matter the cause of your misery, you’ll want to stay clear of the avoidable triggers. So, what can you do if you adore perfumes? What are the common irritants in them? And can you develop a reaction to scents overnight when you’ve been fine all along? We find out.
“The skin’s reaction is to a chemical found in the perfume, and different perfumes contain a different variety of chemicals,” said Dr Foo.
Indeed, there’s quite a bit encapsulated in that tiny bottle. “Typically, fragrances are made up of three layers: Top, middle, and base notes. These layers unfold over time, providing an evolving sensory experience,” said Jason Lee, the founder and CEO of Six Scents.
“The artistry lies in selecting the right combination of ingredients to create a harmonious blend,” he said. “Imagine listening to a song that only has one note; it would be monotonous and lack depth. Fragrance is similar in that it needs layers to create an evolving story.”
Typically, the top notes provide an “initial burst of freshness, like the first few seconds of a song, lasting around 15 to 30 minutes,” said Lee. “The middle notes, or the heart of the fragrance, are what really define its character, lasting two to four hours.” The lasting impression of a perfume is courtesy of its base notes, which can linger for six hours or more, he added.
“Some notes may be derived from natural essential oils, while others are synthetic to enhance stability or uniqueness,” said Lee.
Dr Foo highlighted balsam of peru, isoeugenol and oak moss as potential allergens. For a more comprehensive list of fragrance allergens, the European Union has an updated one last July and manufacturers are required to list those ingredients if they exceed certain concentrations. 
Meanwhile, Lee explained that “skin and nasal allergies often arise from synthetic compounds like artificial musk or preservatives”. “Even some natural essential oils, despite their purity, can be irritants for sensitive skin due to their concentrated nature.” Here are some examples, he said:
Perfumes come in various concentrations to meet different needs, according to Jason Lee of Six Scents.
That’s because allergic contact dermatitis takes time to surface. “Allergic contact dermatitis requires prior sensitisation to the product. Therefore, the first few exposures will not cause a reaction yet,” said Dr Foo.
In other words, said Adj Assoc Prof Leow, you might not have developed any rash when you wore perfumes previously. “But your immune system subsequently recognises perfumes as a noxious agent, thus, developing a rash upon repeated exposure at a later date.”
And if you do have a reaction, an itchy rash (the most common symptom) “may not occur immediately after being sprayed with the fragrance, but it may be delayed by hours or even days”, he said.
Dr Foo advised that if the itch is bearable and the rash does not look too severe, you may be experiencing a mild reaction. “You may be able to avoid medical attention and simply avoid the product in future,” he said.
But if the rash worsens or spreads, consultation with a dermatologist may be warranted, said Adj Assoc Prof Leow.
Both Adj Assoc Prof Leow and Dr Foo said that there is no link between a food allergy and perfume allergy. “A food allergy develops due to the consumption of food proteins. Perfume allergy develops due to contact with chemicals found in perfumes,” said Dr Foo.
“Yes, OTC medication such as a hydrocortisone cream, which is an anti-inflammatory topical steroid, may be sufficient to quell the reaction if it is mild,” said Dr Foo.
But see a GP if the itch is unbearable, the rash is spreading quickly or there are blisters, he said. “You may then be referred to a dermatologist for further treatment and a patch test may be performed if necessary to confirm the allergy.”
Stay away from promoters who try to spray perfumes directly on you. The safest way to test a new fragrance is to ask for a sample to try at home, where you can access medication should you have a reaction, said Dr Foo.
“Test strips are useful for a first impression but a fragrance only truly comes to life on the skin, where it interacts with your body’s natural oils and warmth,” said Lee.
“The best way to test a fragrance is to spray a small amount on your wrist or inner elbow, and let it develop over a few hours. Fragrances evolve with your skin chemistry, so what smells delightful on a paper strip might be quite different on your skin after it has had time to settle,” said Lee.