The word “fragrance” on a product label can represent a blend of dozens to hundreds of individual chemicals. The International Fragrance Association’s 2025 Transparency List catalogues 3,312 ingredients used primarily for their scent properties, plus another 379 functional ingredients like solvents, preservatives, and antioxidants that help a fragrance hold together and last. When a label simply says “fragrance,” any combination of these thousands of approved chemicals could be inside.
The Base: Solvents
Most fragrances start with a solvent that carries the scent molecules and helps them disperse when you spray or apply the product. In perfumes and colognes, the primary solvent is ethanol (alcohol), typically making up more than 70% of the liquid, mixed with water. Ethanol works well because it evaporates quickly, delivering scent molecules into the air, and it dissolves the oily, water-repelling organic compounds that provide most of the smell.
A second common solvent is diethyl phthalate (DEP), an odorless, greasy liquid that shows up in everything from perfumes to household detergents. DEP concentrations in cosmetics range widely, from trace amounts under 0.1% to as high as 28.6% in some fragrance preparations. In finished perfumes sold at retail, concentrations typically fall between 0.25% and 2.5%. Beyond dissolving scent molecules, DEP also works as a fixative, slowing the evaporation of lighter, more volatile notes so the fragrance lasts longer on your skin.
Scent Molecules: Natural and Synthetic
The ingredients that actually produce a fragrance’s smell fall into two broad categories: natural extracts and synthetic compounds. Natural ingredients are typically essential oils distilled from plants, flowers, bark, or resins. A single essential oil is itself a complex mixture, commonly containing 20 to 60 individual chemical components, with two or three dominant compounds making up 20 to 70% of the oil and the rest present in trace amounts. Some oils contain more than 100 distinct substances. Rose oil, for example, gets its scent from a combination of dozens of alcohols, esters, and other organic molecules working together.
Synthetic fragrance ingredients are laboratory-made molecules designed to replicate or improve on natural scents, often at a fraction of the cost. Some are chemically identical to compounds found in nature. Others are entirely novel molecules with no natural counterpart. Synthetic musks are a major example: compounds like galaxolide and tonalide provide the “clean” musky base note in laundry detergents, body washes, and perfumes. These polycyclic musks replaced animal-derived musk decades ago and are now among the most widely used fragrance chemicals in consumer products.
Fixatives: Making Scent Last
Without fixatives, the lightest, most volatile scent molecules in a fragrance would evaporate within minutes. Fixatives are heavier, slower-evaporating substances that interact with those lighter molecules and hold them back, extending how long a fragrance lingers. Some fixatives contribute their own scent: galaxolide and muscone, for instance, serve double duty as both base notes and fixatives. Others, like DEP and benzyl salicylate, work more quietly in the background. Their low volatility and oily nature let them effectively trap and slow-release the more fleeting top notes.
Why Labels Don’t List Individual Ingredients
In the United States, cosmetics sold to consumers must list their ingredients under the Fair Packaging and Labeling Act. But there is a significant exception: fragrance and flavor formulas can be listed as a single word, “Fragrance” or “Flavor,” rather than broken out into their individual components. The legal rationale is that this law cannot be used to force companies to reveal trade secrets, and fragrance formulas, which are complex proprietary blends, are considered the type of cosmetic component most likely to qualify as one.
The European Union takes a different approach. EU cosmetics regulations currently require 26 specific fragrance allergens to be individually named on the label whenever they’re present above certain thresholds. So a product sold in Europe might list ingredients like linalool, limonene, or citronella alongside the generic term “parfum,” while the same product in the U.S. would simply say “fragrance.”
Health Concerns: Allergies and Sensitivity
Fragrance is one of the most common causes of allergic skin reactions from cosmetics. A cross-sectional study across five European countries found that roughly 1.9% of the general population has a confirmed contact allergy to fragrance chemicals, with women affected at about twice the rate of men. That may sound small, but applied to a population of hundreds of millions, it translates to a substantial number of people who develop itchy, red, or blistered skin from products containing fragrance.
Respiratory reactions are also common, particularly among people with asthma. When you inhale fragrance chemicals, they can activate sensory nerve fibers in your nose and airways that respond to irritant vapors. This triggers sensations like burning, tingling, or tightness and can prompt the release of signaling molecules that cause blood vessels in the airways to dilate and glands to increase secretions. For people with asthma, this cascade can provoke symptoms. Even the ethanol base in most perfumes may contribute, since alcohol vapor itself activates these same irritant-sensing nerves. Research also suggests that psychological factors play a role: if someone expects a scent to be harmful, their body may produce a stronger physical reaction to it.
Synthetic Musks and Bioaccumulation
Synthetic musks like galaxolide deserve special attention because of their persistence in the body and the environment. Galaxolide has a high potential to accumulate in fatty tissue. Lab studies on fish have measured bioconcentration factors ranging from 620 in zebrafish to over 1,500 in bluegill sunfish, meaning the chemical builds up in living tissue at concentrations far higher than in the surrounding water.
Several studies have found that galaxolide and the related compound tonalide show weak hormonal activity. In laboratory settings, both bind to estrogen receptors (though with low affinity) and can slightly stimulate or, paradoxically, inhibit estrogen-related activity depending on the conditions. They’ve also been shown to suppress the activity of androgen and progesterone pathways and to decrease production of progesterone and cortisol in human cell lines. None of these effects have been dramatic in isolation, but their presence in products used daily and their tendency to accumulate in the body have kept them on the radar of biomonitoring programs, including California’s.
What “Fragrance-Free” and “Unscented” Mean
These two terms are not the same. “Fragrance-free” generally means no fragrance chemicals were added to the product at all. “Unscented” means the product has no noticeable smell, but it may still contain fragrance chemicals used specifically to mask the odor of other ingredients. An unscented lotion, for example, might include masking fragrances that neutralize the natural smell of its base ingredients. If you’re trying to avoid fragrance chemicals entirely because of skin sensitivity or respiratory concerns, “fragrance-free” is the more reliable label to look for.