Why More Ingredients Do Not Necessarily Smell Stronger
Updated: Oct 20
Fragrance intensity invites a simple arithmetic intuition: if one smell has strength and another smell has strength, combining them should produce the two strengths added together.
Human odor perception does not reliably follow that arithmetic.
In controlled psychophysical studies, mixtures can be hypo-additive: their total perceived intensity can fall below the arithmetic sum of the components measured separately. In Laing and colleagues’ study of binary odor mixtures, the tested mixtures showed that pattern. [1]
That does not mean mixtures are inherently weak or that adding an odorant always lowers intensity. It means “more ingredients = more scent” and “more ingredients = less scent” are both unreliable shortcuts.
The evidence is about non-additivity, not a universal direction of change.
A note on the word “ingredients”
The research here uses defined odorants in controlled mixtures. “Ingredients” is everyday language for the intuition under examination; these studies do not count materials in a commercial fragrance formula and predict finished perfume or candle strength.
The supported claim is therefore about perception of controlled odor mixtures—not a formula-count rule for products.
Intensity is not simple arithmetic
Suppose odorant A and odorant B are each rated separately. A simple additive model would predict that the mixture should equal the sum of those two ratings.
In Laing and colleagues’ tested binaries, total mixture intensity was below the summed component intensities, and relative component intensity also influenced what participants perceived. [1]
That pattern is commonly described as hypo-additivity or intensity suppression.
Here, “suppression” is relative to an additive prediction. A hypo-additive mixture is not necessarily weaker than every component alone; it simply does not behave like independent intensity values added together.
So an additional odorant is not automatically another notch on a volume control.
What happens as mixtures become more complex?
A second classic study asked observers to rate five odors and mixtures containing two through five components. Those mixtures showed moderate intensity suppression, and a model that worked reasonably for binaries overpredicted intensity for mixtures with more components. [2]
The limit is crucial: component count was not isolated from component identity or composition.
The study therefore does not give us a strength curve by ingredient count. It shows that a model derived from simpler mixtures did not scale cleanly to more-complex ones.
Component count alone cannot tell you how intense a mixture will smell.
One demonstrated route to suppression
Mixture interactions can arise at multiple levels, so no single mechanism explains every fragrance.
Fukutani and colleagues provide one especially clear, narrow example. Receptor assays identified antagonistic interactions; in human sensory testing, β-ionone reduced the perceived intensity and unpleasantness of methanethiol when delivered as a mixture. The same suppression was not reproduced when the two odorants were delivered to different nostrils. [3]
That is evidence for an interaction in one defined system—not a universal law of perfumery and not evidence that receptor antagonism explains every case of mixture suppression.
Nor does it show the odorants chemically reacting to create a new substance. The finding is a change in sensory response when they are presented together.
What ingredient count cannot tell you
Which odorants are present or how intense they are relative to one another.
Whether the tested mixture will behave additively, hypo-additively or show component-specific suppression.
Whether a specific interaction like receptor antagonism is relevant to that particular mixture.
Whether changing the delivery conditions will change the observed interaction.
Component count describes how many components are in an experiment. It cannot substitute for their identities, relative intensities, concentrations or presentation conditions.
Why this does not become a candle-strength rule
None of the three studies cited here is a Pruneme candle test, and none establishes that adding more fragrance materials makes a candle’s hot throw weaker, stronger or unchanged.
The defensible transfer is narrower: human odor mixtures can be non-additive, so component count alone is not a reliable shortcut for perceived strength.
Candle performance is a separate product question. For candle-specific language and testing concepts, see Cold Throw vs Hot Throw (Why They Don’t Match) and What “Hot Throw” Really Means (And What It Doesn’t).
This article therefore stays away from fragrance-load percentages, wax comparisons, wick behavior and commercial blending instructions. Those would require product-specific evidence, not an extrapolation from odorant psychophysics.
A better question than “How many ingredients?”
A better perceptual question is not whether a fragrance has “more” ingredients, but what its components do together under the conditions in which they are smelled.
Mixture intensity can fall below an additive prediction. [1] A model that worked reasonably for binaries can overpredict more-complex mixtures. [2] In one defined sensory system, one odorant suppressed another. [3]
Together, those findings do not make ingredient count useless as a description; they make it unreliable as a strength meter.
Reader takeaway
More ingredients do not necessarily smell stronger—or weaker.
The evidence supports the narrower conclusion that mixture intensity depends on interactions among components and the conditions of presentation, so simple arithmetic and component counts can fail.
“How many ingredients?” is therefore the wrong shortcut for “How strong will this smell?”
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