Considerably more people than previously believed are allergic to the most common fragrance ingredient used in shampoos, conditioners and soap. A thesis presented at the Sahlgrenska Academy, University of Gothenburg, Sweden found that over 5% of those who underwent patch testing were allergic to the air oxidized form of the fragrance ingredient linalool.
"I would suspect that about 2% 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 found in 60-80 percent of the perfumed hygiene products, washing up liquids and household cleaning agents that can be bought in the nearest supermarket, and it can be difficult for people who are allergic to avoid these products", says dermatologist Johanna Bråred Christensson, author of the thesis.
Around one person in five in Sweden has some form of contact allergy. Nickel is by far the most common substance that causes eczema, but the thesis shows that oxidized linalool occupies third place in the list, after nickel and cobalt.
In the study, oxidized linalool was added at patch testing for more than 3,000 patients who wanted to find out what was causing their eczema. Between 5% and 7% proved to be allergic to the oxidized form of the 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 t! he substance increases", says Johanna Bråred Christensson.
Linalool is a fragrance ingredient found naturally in lavender, mint, and other plants. Linalool breaks down when it comes into contact with oxygen, it becomes oxidized and can cause allergy. Manufacturers do include other substances in the products to delay this oxidation process, but allergenic substances can st! ill be formed from linalool when it is stored.
"One way of trying to minimize exposure to oxidized linalool is to avoid buying large packs of soap and shower cream, and always to replace the top after using a bottle", says Johanna Bråred Christensson.!
EU legislation states that manufacturers must specify on the labels of hygiene products whether they contain linalool. Previous studies have shown that oxidized linalool may cause contact allergy in about 1% of patients with eczema.
BRIEF FACTS: COMMON CONTACT ALLERGENS
Around 10-15% of all Swedes are allergic to nickel, and this is the ! most common form of contact allergy. Another substance that may be present in imitation jewellery is cobalt, to which around 2 3% of the population is allergic. Linalool occupies third place in the list after nickel and cobalt. It has been estimated that 2% of all Swedes are allergic to linalool. Other substances that can cause contact allergy include various perfumes and preservatives.
The Sahlgrenska Academy
The Sahlgrenska Academy is the faculty of health sciences at the University of Gothenburg. Education and research are conducted within the fields of pharmacy, medicine, odontology and health care sciences. About 4000 undergraduate students and 1000 postgraduate students are enrolled at Sahlgrenska Academy. The staff is about 1500 persons. 850 of them are researchers and/or teachers.
This thesis is based on the following papers:
I. Air oxidation increases skin irritation from fragrance terpenes Bråred Christensson J, Forsström P, Wennberg A-M, Karlberg A-T, Matura M. Contact Dermatitis: 2009: 60: 32-40.
II. Oxidized linalool - a significant contact sensitizer Bråred Christensson J, Matura M, Gruvberger B, Bruze M, Karlberg A-T. Manuscript.
III. Hydroperoxides form specific antigens in contact allergy. Bråred Christensson J, Matura M, Bäcktorp C, Börje A, Nilsson JLG, Karlberg A-T. Contact Dermatitis: 2006; 55(4): 230-7.
IV. Limonene hydroperoxide analogues differ in allergenic activity. Bråred Christensson J, Johansson S, Hagvall L, Jonsson C, Börje A, Karlberg A-T. Contact Dermatitis: 2008; 59(6): 344-52.
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