Can a fragrance-free product have a smell? Absolutely. Can an unscented product contain any compounds that have a smell? Absolutely. It’s all a matter of semantics although there are no universally recognized definitions here. Unscented products are formulated to have no smell but can contain ingredients that have a smell but the smell has been neutralized by other components. A fragrance-free product cannot contain any ingredients that have been added to impart a smell but may contain ingredients that have a scent but are not added because of their scent. For example if a cream is made with an oil that has a smell, it could still be labeled as fragrance-free because the purpose of the oil is to act as an emollient, not as a scent. But it could not be labeled unscented. However, if a product is formulated with lavender, for example, but some chemical is added to mask the smell, the product can be labeled as “unscented.”
This type of terminology is important to understand because someone who is allergic to lavender, for example, can still be allergic to a product in which the smell is masked, but they may not realize that the allergen is present because of the unscented designation.. In general, fragrances are added to make a consumer product more appealing, or in some cases, to trigger a physiological reaction. Fragrances can be categorized as “essential oils,” as “natural” or as “synthetic.” Essential oils are complex mixtures that are isolated from plant sources. Natural fragrance molecules are single molecular entities derived from a natural source. For example geraniol, extracted from roses would be a natural fragrance. But geraniol synthesized in the lab would be a synthetic fragrance even though it is exactly the same substance. Of course you can also have fragrances that are synthetic molecules not found in nature at all.
Fragrances in consumer products can be made up of literally hundreds of components, both natural and synthetic. The individual compounds do not have to be listed by name on labels. Unfortunately some of these can cause adverse reactions in people, especially if they already suffer from some sort of respiratory problem. They can also react with ambient compounds in the air to generate secondary pollutants. For example compounds such as limonene and pinene used to impart lemony or pine odours to cleaning agents or air fresheners can react with indoor ozone to produce formaldehyde, glycol ethers or hydroxyl radicals which are all irritants. Most people of course are not at risk, but asthmatics can react.
Sometimes fragrances serve a purpose other than just imparting a pleasant smell. When infants are bathed in fragranced bath products, there is an increase in infant-mother engagement. Somehow the scent reinforces the infant-mother bond. There’s another possible benefit. In one study, infants bathed with fragrant products spent less time crying before falling asleep and had deeper sleeps than babies bathed with unscented products. Unfortunately it is also possible for babies to develop allergic reactions to fragrances. But over the years the most likely fragrance molecules that can cause allergic reactions have been identified and are not used in baby products. In the European Union 26 fragrance molecules have been identified as potential allergens and must be identified on labels if they are used above a specified level.