Common Fragrance Ingredient is a Potent Allergen

A thesis presented at the Sahlgrenska Academy, University of Gothenburg, Sweden suggests that linalool, a common fragrance ingredient in personal care products and household products, instigates allergic skin reactions in considerably more people than was previously thought to be the case.

Linalool is a colourless fragrant terpene found in various plants e.g. lavender, rosewood. It is also synthetically manufactured to cut costs and used in household and hygiene products as a fragrance chemical. The concentrations used in cosmetics are fairly low but in aromatherapy products, natural products and in homemade soaps and fragrances, higher concentrations are often used.

When linalool is exposed to air with normal handling autoxidation occurs, forming allergenic oxidation products, in particular hyperoxides which are the most potent allergens.

The fragrance terpene limonene (the main constituent of peel oil from citrus fruits), commonly used in consumer products also becomes more irritating following exposure to air. Other terpenes can also cause allergic reactions on contact with oxygen. It is not the pure compounds that instigate a strong reaction but the oxidation products.

Scientists have already identified nickel and cobalt as the most common substances responsible for eczema and this study places linalool third on the list.

In the University of Gothenburg study 3,418 patients already suffering from dermatitis were given an oxidized linalool patch, with 5-7 percent of the patients demonstrating an allergic reaction to the substance.

Johanna Brared Christensson, dermatologist and author of the thesis says that Linalool is found in 60-80 percent of perfumed hygiene products, making it difficult to avoid for individuals suffering from the allergy.

“I would suspect that about 2 percent of the complete population of Sweden are allergic to air oxidized linalool. That may not sound very much, but it is serious since linalool is so widely used as a fragrance ingredient.”

“Linalool is present in many products around us, and this is probably the reason that contact allergy to this material is so common. Some people can shower with shower cream that contains linalool but never develop contact allergy, but we know that the risk increases as the exposure to the substance increases”, says Johanna.

Joanna suggests that if you use a product that includes linalool, make sure you replace the cap after use, because it is when linalool is exposed to air that it becomes an allergen. She also urges people to avoid purchasing large packs of soap and showering cream because allergenic substances can be formed from linalool when it is stored.

The thesis concludes that “seemingly harmless products may cause or worsen ACD (allergic contact dermatitis)” and therefore “it is important to study the contact allergenic potential of chemicals to which we are exposed.”

EU legislation states that manufacturers must specify on the labels of hygiene products whether they contain linalool, so if you wish to avoid products containing this substance always read the ingredients labels.

Source: Science Daily

Johanna’s Thesis