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Cetyl alcohol is a fatty alcohol that appears as a white, waxy solid in flake or powder form. It was originally discovered in 1813 by the French chemist Michel Chevreul, who obtained it by saponifying spermaceti, a wax-like substance obtained from sperm whale head oil.
Cetyl alcohol is a multifunctional cosmetic ingredient and is used as a emollient, emulsifier, emulsion stabilizer, foam booster, masking agent, opacifier, surfactant and viscosity control agent. In 2006, cetyl alcohol was reportedly used in 2,931 cosmetic products, with data from 2005 indicating that it was included up to a concentration of 15%.
Cetyl alcohol has a relatively low molar mass and is oil-soluble, which may enable it to pass through the stratum corneum. It has been mentioned that cetyl alcohol penetrates the skin like active substances. A paper published in 1985 stated that it was unlikely that cetyl alcohol penetrates intact skin in allergicologically relevant concentrations but that a marked percutaneous absorption is expected with diseased skin. Unfortunately, we were unable to obtain any further details on the experiments conducted to reach this conclusion.
Another paper described a water-in-oil microemulsion that was able to deliver cetyl alcohol into the skin 2-6 times faster and at least twice as much as 2 macroemulsion formulations, namely a cream and a lotion.
Interestingly, cetyl alcohol can act as a penetration enhancer. It moderately enhanced the penetration of the pain reliever fentanyl and the vasodilator nitroglycerin, from drug-in-adhesive patches into excised rat abdominal skin in 2 separate studies.
If cetyl alcohol is able to reach viable skin, it may be oxidized to palmitic acid by the enzyme fatty alcohol:NAD+ oxidoreductase in human fibroblasts, as has been shown to occur in vitro. The palmitic acid so formed may then become part of the skin barrier, since palmitic acid is known to be a component of the epidermis.
3. Effects on the skin
3.1 Increased hydration
Cetyl alcohol is said to be used as an emollient to prevent skin from drying and chapping because of its water-binding property. It has also been lumped together with occlusive moisturizing ingredients such as petrolatum, lanolin and mineral oil elsewhere. We were not able to find any experimental data to substantiate these claims however, save for one study which found that a combination of cetyl alcohol, isostearyl isostearate, potassium cetyl phosphate, cetyl behenate and behenic acid improved the visible signs of skin dryness more effectively than a comparable vehicle containing mineral oil.
3.2 Psoriasis treatment
Cetyl alcohol has apparently been tested for its effects on psoriatic scales, but no further information was available.
4. Side Effects
Cetyl alcohol was first assessed by the Cosmetic Ingredient Review (CIR) Expert Panel in 1988, which concluded that it was safe for use. In 2005, the CIR Expert Panel evaluated new data that had become available since the first review, and reaffirmed its original conclusion.
4.1 Dermal toxicity
When cetyl alcohol was applied full-strength to the clipped intact or abdominal skin of rabbits, one of the four animals dosed with 3.16 ml/kg (the highest dose tested) had decreased activity and laboured respiration. The acute dermal toxicity was reported to be > 2.6 g/kg in this study, and > 2 g/kg in another similar study.
Subchronic dermal toxicity studies have also been performed. In one, 30% cetyl alcohol in methanol and propylene glycol was applied to 5 rabbits daily for 30 days, after which infiltrates of lymphomononuclear cells and histiocytes were observed in the superficial portions of the dermis. 2 other studies utilized creams containing 11.5% cetyl alcohol, which was applied 5 times daily to 20 and 48 rabbits for 20 days. All the rabbits developed visible signs of exfoliative dermatitis within 2-3 days, characterized by acanthosis, parakeratosis, hyperkeratosis, and papillary projections of the epidermis. A 3-month dermal toxicity study, also on rabbits, of a moisturizer containing 2% cetyl alcohol found only mild inflammation at the application site however, and no evidence of systemic toxicity.
4.2 Skin irritation and sensitization
Animal studies concur that cetyl alcohol has low skin irritation potential, reporting either no irritation or only very slight to well-defined erythema, slight to mild edema and slight desquamation even when 100% cetyl alcohol was applied under occlusive conditions for 24 hours.
Cetyl alcohol has also been tested extensively for its skin irritation and skin sensitization potential in humans. Of the human studies submitted to the Cosmetic Ingredient Review Expert Panel for its initial safety assessment, the vast majority were unpublished experimental data on cosmetic products such as creams, lotions, lipsticks, cleansers and conditioners, that contained low concentrations (<10%) of cetyl alcohol. All identified no or only slight irritation and/or sensitization, and 2 concluded that products containing 1% and 4% cetyl alcohol did not induce photosensitization. When 82 patients in Colombia who had suspected photoallergic contact dermatitis were patch-tested, only 1 had a positive contact reaction to cetyl alcohol.
Although one study analyzing the results of 3 years of patch tests in 330 dermatological patients revealed that 11.2% had allergic reactions to cetyl alcohol, the authors acknowledged that this figure was not consistent with those from other studies in the literature. For example, Hjorth and Trolle-Lassen identified only 2 positive reactions among 1,664 consecutive patients, while Fisher et .al. did not identify any positive reactions among 100 patients. It has been suggested that the anomalously large number of positive patch tests in the first study may be due to the preferential choice of creams containing cetyl alcohol for the treatment of outpatients.
This agrees with the case reports in the literature of contact allergy and contact dermatitis to cetyl alcohol, most of which were due to its presence in topical medications and only a few of which were attributed to cetyl alcohol-containing cosmetic products.
Paradoxically, paraffin wax in cetyl alcohol has been found to statistically significantly reduce allergic rashes produced by the oil urushiol, a condition termed Rhus allergic contact dermatitis.
A paper published in 1989 classified cetyl alcohol as moderately comedogenic, with a grade of 2 out of 5 for comedogenicity, indicating that it caused a moderate increase in follicular keratosis when applied daily 5 days per week for 2 weeks to rabbit ear skin. A more recent study also using the rabbit external ear canal found that cetyl alcohol was not comedogenic, however.
4.4 No evidence of mutagenicity
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