Synthetic fragrance is any scent created in a laboratory rather than extracted directly from a plant, animal, or mineral source. Most synthetic fragrances are derived from petroleum, and a single “fragrance” listed on a product label can contain dozens to hundreds of individual chemical compounds. These lab-made scents appear in perfumes, cleaning products, candles, laundry detergent, shampoo, lotion, and air fresheners.
What Synthetic Fragrances Are Made Of
The chemical building blocks of synthetic fragrance span a huge range of organic compounds: alcohols, aldehydes, esters, ketones, ethers, nitrogen-containing ring structures, and hydrocarbons, among others. In nature, a floral scent might require dozens of molecules working together. A lab can replicate that scent, or invent an entirely new one, sometimes with just a single molecule. This is one reason synthetic fragrances dominate the market: they’re cheaper to produce, more consistent batch to batch, and far more versatile than anything harvested from flowers or bark.
Synthetic fragrances also tend to last longer on skin and fabric. That staying power comes partly from the scent molecules themselves but also from fixatives, chemicals added specifically to slow evaporation. The most common fixatives in personal care products are phthalates, particularly diethyl phthalate (DEP) and dimethyl phthalate (DMP). These odorless chemicals act as solvents and anchors, letting a perfume or cologne release its scent gradually over hours instead of fading within minutes. Phthalates show up in perfumes, colognes, deodorants, shampoos, soaps, and nail polishes.
Another major category is synthetic musks. Natural musk originally came from animal glands, but nearly all musk in modern products is synthetic. These compounds are lipophilic, meaning they dissolve easily in fats and persist in biological tissue for a long time.
Why You Can’t Tell What’s Inside
In the United States, the FDA allows manufacturers to list the word “fragrance” (or “flavor”) as a single ingredient on a label, without disclosing any of the individual chemicals that make up that scent. This is a trade-secret protection: fragrance formulas are considered proprietary. A product listing “fragrance” among its ingredients could contain 10 chemicals or 300, and you’d have no way to know from the label alone. Manufacturers can choose to list fragrance ingredients individually, but very few do.
This matters because a survey of common scented consumer products found that each one emitted between 1 and 8 chemicals classified as toxic or hazardous under federal law. Close to half of the products tested generated at least one carcinogenic air pollutant, including formaldehyde, acetaldehyde, and methylene chloride. None of these appeared on the label.
Skin Reactions and Allergies
Fragrance is one of the most common causes of allergic contact dermatitis. Dermatologists have identified more than 30 individual fragrance chemicals that trigger skin reactions in a significant number of people. The worst offenders include cinnamal, isoeugenol, hydroxycitronellal, and a compound called HICC (sold under the brand name Lyral), which was eventually pulled from the market in the EU because of its high sensitization rate.
Two common natural-sounding ingredients, limonene (citrus scent) and linalool (floral scent), cause relatively few problems in their pure form. But when exposed to air, they oxidize into new compounds called hydroperoxides, and those breakdown products are potent allergens. This means a product can become more irritating over time as it sits on a shelf or in a bathroom cabinet.
Skin reactions to fragrance don’t always appear immediately. Some people develop sensitivity after years of problem-free use, and the reaction can show up as redness, itching, or a rash anywhere the product touched skin, or even in areas it didn’t.
Effects on Indoor Air
Scented products are a significant source of volatile organic compounds (VOCs) indoors. One analysis of popular air fresheners, laundry products, and cleaners found they collectively emitted more than 100 different VOCs. The most frequently detected were limonene, alpha- and beta-pinene (pine scents), ethanol, and acetone. Some of these compounds react with ozone already present in indoor air to form secondary pollutants, including formaldehyde, a known carcinogen.
In U.S. telephone surveys, about 19% of respondents reported health problems they attributed to air fresheners, and roughly 11% reported irritation from scented laundry products vented outdoors through dryer exhaust. Reported symptoms ranged from headaches and respiratory irritation to more severe neurological reactions.
Hormonal Concerns
Some synthetic fragrance ingredients can interact with hormone receptors in the body. Synthetic musks like musk xylene and musk ketone have shown weak estrogenic activity in lab studies, meaning they can mimic estrogen at the cellular level. In one experiment, musk ketone increased the proliferation of human breast cancer cells by 97% compared to controls. When an anti-estrogen drug was added, this effect disappeared, confirming the growth was driven through estrogen receptors.
In human studies, blood levels of musk xylene were inversely associated with progesterone and estrogen during the luteal phase of the menstrual cycle, suggesting these compounds may interfere with the hormonal signaling between the brain and the ovaries. Phthalates used as fragrance fixatives have also raised concern as potential endocrine disruptors, though their effects depend heavily on the type and amount of exposure.
Environmental Persistence
Synthetic musks don’t break down easily. German researchers found musks in the body fat of every person they tested, concluding that humans are constantly exposed to these highly stable compounds. The chemicals also concentrate in breast milk.
In aquatic environments, the picture is troubling. Researchers at Stanford found that synthetic musks impaired a key defense system in California mussels. Healthy cells use a kind of molecular pump to flush out toxic substances. Mussels exposed to common synthetic musks lost 38 to 84% of this pumping ability, meaning toxins that would normally be expelled accumulated inside cells instead. The most striking finding was that this damage persisted long after the musk exposure ended. Tissue treated with musk xylene, musk ketone, and two other widely used compounds remained compromised 48 hours later. This suggests that synthetic musks don’t just pose a direct toxic threat; they may also make organisms more vulnerable to other pollutants in the water.
Industry Self-Regulation
The fragrance industry largely polices itself through the International Fragrance Association (IFRA), which sets safety standards for how much of a given ingredient can appear in finished products. IFRA bases its standards on safety assessments reviewed by an independent expert panel. Some ingredients are banned outright, others are restricted to specific concentrations, and some must meet purity criteria. Compliance is mandatory for IFRA members, which represent roughly 80% of global fragrance production by volume. The remaining 20% operates outside this framework.
In the EU, cosmetics regulations require 26 known fragrance allergens to be listed individually on labels when they exceed certain concentrations. The U.S. has no equivalent requirement.
Fragrance-Free vs. Unscented
If you’re trying to avoid synthetic fragrance, the label language matters. “Fragrance-free” means no fragrance materials or masking scents were added to the product. “Unscented” means something different: the product may still contain fragrance chemicals, but they’ve been added specifically to neutralize or cover up the smell of other ingredients. An unscented lotion, for example, might contain masking agents that technically qualify as fragrance compounds.
The EPA’s Safer Choice program offers a fragrance-free certification that verifies a product contains no chemicals that impart or mask a scent. For anyone with fragrance sensitivity or allergy concerns, this certification is more reliable than the word “unscented” on its own.