Hydroxyisohexyl 3-cyclohexene carboxaldehyde, also known as
Lyral, is a fragrance ingredient identified as the cause of contact
allergic reactions in 2-3% of
eczema patients undergoing patch testing.
Lyral has been included in the standard patch test series in many clinics due to its importance as an
allergen. It has been used without restrictions in cosmetic products, until now. In the present study, the dose-response relationship of
Lyral contact
allergy was studied with doses relevant for normal exposure in cosmetic products. 18
eczema patients, who previously had given a positive patch test to
Lyral 5%
petrolatum, were included along with 7 control subjects. All cases were tested with a serial dilution of
Lyral in
ethanol 6% to 6 p.p.m and subjected to a 2-week, repeated open application test with a low dose of
Lyral in
ethanol. In the case of no reaction, this was followed by another 2 weeks of testing with a higher dose. The test was performed at the volar aspect of the forearm. In 16 of 18 cases (89%), a positive use test developed, 11 reacting to the low and 5 to the high concentration. None reacted to the vehicle control of
ethanol applied to the contralateral arm. All controls were negative to both the test solutions of
Lyral and the
ethanol control. The difference between the test and the control group was statistically significant (Fisher's test, P < 0.001). It is concluded that
Lyral at the current usage levels is inducing sensitization in the community. The same levels were shown to elicit
allergic contact dermatitis in almost all sensitized individuals. A significant reduction in usage concentrations is recommended to prevent contact
allergic reactions.