A decade ago, Corinne Segura was an active 29-year-old who enjoyed dancing and cycling. But, after exposure to mould in her rented home, she began having strange symptoms. Whenever Corinne was around certain very common chemicals – air fresheners, household pesticides, new carpet in a doctor’s office, petrol station pumps, even essential oil diffusers – she became dizzy, disoriented and exhausted, and her throat would swell up. The symptoms became so debilitating that she eventually had to quit her job as a financial grant writer and move.

Doctors prescribed antihistamines and an asthma inhaler, but the only thing that helped was avoidance. “The more I removed chemicals from my space, the simpler it was to tell which products bothered me,” Corinne says. After several years of this and taking supplements prescribed by a naturopath, Corinne has greatly improved. But her recovery hasn’t been a straight line: When smoke from bushfires a few years ago wafted her way, her sensitivities revved back up. Recently, she says, she was stuck in fumy traffic and had to spend a whole day recovering in bed.

Although Corinne has never been diagnosed, it appears that she suffers from a condition known as multiple chemical sensitivity (MCS). Others call it chemical intolerance, idiopathic environmental intolerance (IEI) or, when there’s an identifiable initiating exposure, toxicant-induced loss of tolerance (TILT). And the condition is more common than many realise. The most recent Australian survey found that 18.9 per cent of people experience symptoms from everyday chemicals and chemically formulated products, while 6.5 per cent report medically diagnosed MCS, with symptoms including migraines, skin rashes, brain fog, nausea and even fainting or seizures. And the problem seems to be growing, or at least it’s better recognised than it once was: Rates of diagnosed chemical intolerance have risen 300 per cent in the past decade, according to the University of Melbourne.

MCS is thought to begin when someone encounters an irritating chemical either in one gulping dose (such as during a raging fire) or from smaller but more lasting encounters, like the mould in Corinne’s house. Once this happens, certain people can become sensitive to many fragrances. Scientists don’t fully understand MCS, and not all doctors even accept that it exists. But a growing number are aiming to better grasp how contact with chemicals at levels considered safe can bother or debilitate so many, says allergy specialist Dr Jonathan Bernstein, who sees many patients with the condition.

In some ways, chemical intolerance is similar to an allergy. When someone becomes allergic to, say, peanuts, contact with even a tiny amount creates a disproportionate reaction across the body. But MCS isn’t an allergy, because it doesn’t cause the body to produce antibodies known as immunoglobulin E (IgE) as in an allergic reaction. For this reason, some doctors turn away people who complain of these symptoms because they don’t know exactly how to help them, Dr Bernstein says.

Smells like trouble

Sensitivities can be initially caused or later triggered by a range of common factors. Here are the main ones.

Office and Home Materials 

These may be brimming with airborne chemicals – new furniture and flooring are two examples. That ‘new car smell’ is actually formaldehyde and a soup of other volatile substances, says Dr Gediminas Mainelis, a professor of environmental sciences. New or renovated buildings create some of the biggest problems. Even ‘green’ buildings aren’t exempt, because the tight seals created around doors and windows to improve energy efficiency may trap gases and particles inside and worsen indoor air if ventilation is inadequate, Dr Mainelis says.

Fragranced Products 

This is one of the most common triggers, according to research by Dr Anne Steinemann, a professor of civil engineering at the University of Melbourne. A single scented household or personal care product typically gets its smell from dozens of ingredients, most of which need not be listed on the label. Any of these substances might set off a reaction.

Pesticides and Insecticides

Even a single application of indoor pesticides has been known to initiate chemical intolerance, says Dr Claudia Miller, an allergist/immunologist specialising in environmental medicine. So, sufferers can be triggered when staying in houses or hotels where these are sprayed. Often people can’t put their finger on exactly which chemicals make them sick, Dr Miller says, and some that don’t even have smells can be triggers. Furthermore, symptoms such as headaches may be chalked up to stress when they’re actually due to a chemical trigger. The quantity of chemicals we’re all exposed to has increased exponentially over the years, Dr Bernstein says. “Some people are bothered by this more than others,” he adds.

Cigarette Smoke 

Burning cigarettes emit a wide range of harmful chemicals, including benzene and lead. “We’ve measured 10 times higher particle mass concentrations inside smokers’ homes compared with non-smokers,” Dr Mainelis says. E-cigarette users aren’t any safer. In fact, they’re exposed to not only nicotine, but also ultra-fine particles, volatile organic compounds and other chemicals.

How To Reduce Scents In Your Environment 

These steps will help people with MCS as well as allergies and other ills.

  • Reduce air fresheners in your home, car and office. Even items with pretty fruits or flowers on their labels get their scents from chemicals. Essential oil diffusers bother some people, too.
  • Choose the right filter in your air purifier. Carbon-and zeolite-based filters quell odours and chemical irritants, Dr Bernstein says. Opening windows, if the weather allows, may also help.
  • Keep laundry fragrance free. Because they leave your home through dryer vents, chemicals in laundry products become ‘secondhand scent’ to others.
  • Limit perfume use. So many people are sensitive that some health bodies recommend that everyone shun perfume, cologne, aftershave and scented lotions and hairsprays at the office.

On The Trail

Not having the scientific knowledge of what’s going on [in the body of someone with MCS] is what causes some doctors to tell patients that it’s not a real problem; that it’s all in their head,” says MCS researcher and psychiatrist Dr Thomas Uhde. But experts do have some idea of what’s happening inside your body.

Immunity Glitch 

Immune cells, known as mast cells, are created in the bone marrow before spreading through the body to repel invaders. Dr Miller believes mast cells that are erroneously called up, even when chemicals aren’t dangerous, cause the wide-ranging reactions.

The Nocebo Effect 

Some experts suggest that people become intolerant to chemicals when symptoms are linked in the brain with certain smells (the opposite of the placebo effect). Then, when the person later experiences those odours, their body sets off a reaction. “Nocebo symptoms are real; it’s people’s attributions of the symptoms to environmental factors that’s wrong,” notes Dr Omer Van den Bergh, a psychology professor who published this theory in the journal Clinical Psychological Science.

Negative Association 

“If you have a traumatic experience that involves an odour in the environment, an association is going to be laid down,” which is helpful from an evolutionary perspective to keep you from danger, says psychiatrist Dr Bernadette Cortese, who works with Dr Uhde. The pair hypothesise that, especially in people with certain kinds of anxiety, a traumatic or chronic stress involving a smell might then increase sensitivity to other odours that are strong, acidic or burning (the
kinds most likely to be hazardous). In a study they published in 2018, people with anxious personalities were more bothered by a smoky smell (one of these so-called ‘trigeminal odours’) than other people were. Meanwhile, a roselike scent didn’t faze them.

Breathing Easier

Treatments currently being tested follow from these theories. Dr Uhde and Dr Cortese found in a small study that a brief stint of cognitive behavioural therapy (CBT) reduced overall sensitivity to smells in those with high anxiety. Dr Miller advocates medicines that target mast cells. Blocking histamine receptors with allergy or gastrointestinal intolerance (GI) drugs can sometimes also help, she says. And Dr Van den Bergh created a treatment in which patients are coached on how to disrupt nocebo reactions.

But, until a treatment is proven to work in large clinical trials, people with MCS are left to figure it out for themselves. The majority aim to eliminate chemicals from their life, something that’s very hard because chemicals are everywhere. Still, the effort is worth it: One study from the University of Melbourne found that when air fresheners were taken out of office bathrooms, chemical concentrations in the air dropped by up to 96 per cent within two weeks.

Corinne, for her part, grew into such an expert on minimising chemicals in her home that she became a consultant, educating others with MCS and other respiratory illnesses about the ideal materials to use in their spaces. (Hint: Vinyl and laminate flooring aren’t among them.)

“Most people who are sensitive lead strict lives in order to survive and function, but that can’t be the answer,” Dr Cortese says. “We need to find ways to treat them by better understanding the biological basis and studying which interventions are helpful.”

Until then, Dr Steinemann believes that everyone can help by reducing the mix of scented products that surround us. “People with chemical sensitivities are like human canaries,” she says. “They react earlier and more severely to chemical pollutants, even at low levels.”

Originally published in May 2022 issue of Prevention US.

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