Lanolin - Modern Developments

Modern Developments

In addition to general purity requirements, lanolin must meet official requirements for the permissible levels of pesticide residues. The Fifth Supplement of the United States Pharmacopoeia XXII published in 1992 was the first to specify limits for 34 named pesticides. A total limit of 40 ppm (or mg/kg) total pesticides was stipulated for lanolin of general use, with no individual limit greater than 10 ppm.

A second monograph also introduced into the US Pharmacopoeia XXII in 1992 was entitled 'Modified Lanolin.' Lanolin conforming to this monograph is intended for use in more exacting applications, for example on open wounds. In this monograph, the limit of total pesticides was reduced to 3 ppm total pesticides, with no individual limit greater than 1 ppm.

In 2000, the European Pharmacopoeia introduced pesticide residue limits into its lanolin monograph. This requirement, which is generally regarded as the new quality standard, extends the list of pesticides to 40 and imposes even lower concentration limits.

However, some very high purity grades of lanolin surpass monograph requirements. New products obtained using complex purification techniques produce lanolin esters in their natural state, removing oxidative and environmental impurities resulting in white, odourless, hypoallergenic lanolin. These ultra-high purity grades of lanolin are ideally suited to the treatment of dermatological disorders such as eczema and on open wounds.

Some years ago, lanolin attracted a great deal of attention owing to a misunderstanding concerning its sensitising potential. A study carried out at New York University Hospital in the early 1950s had shown about 1% of patients with dermatological disorders were allergic to the lanolin being used at that time. However, this figure was misinterpreted and taken out of context and became quoted as 1% of the general healthy (American) population. By one estimate, this simple misunderstanding of failing to differentiate between the general healthy population and patients with dermatological disorders exaggerates the sensitising potential of lanolin by 5,000–6,000 times.

By the time the European Cosmetics Directive was introduced in July 1976, so much adverse (but completely unfounded) publicity concerning lanolin had occurred, it contained a stipulation that cosmetics which contained lanolin should be labelled to that effect. This ruling was challenged immediately, and in the early 1980s, it was overturned and removed from the directive. Despite only being in force for a very short period of time, this ruling did a great deal of harm both to the lanolin industry and to the reputation of lanolin in general. The irony is that the Cosmetics Directive ruling only applied to the presence of lanolin in cosmetic products; it did not apply to the many hundreds of its different uses in dermatological products designed for the treatment of compromised skin conditions.

However, lanolin's safety and efficacy are probably best illustrated by taking a look at the market. High lanolin content baby care products (some as high as 100%) and treatment products for nursing mothers are commonplace.

More recently, using modern scientific methods, attention has focused on the positive aspects of lanolin and on increasing the understanding about how lanolin achieves its beneficial skin effects.

Modern analytical methods have revealed lanolin possesses a number of important chemical and physical similarities to human stratum corneum lipids; the lipids which help regulate the rate of transepidermal water loss and govern the hydration state of the skin.

Cryogenic scanning electron microscopy has shown that lanolin, like human stratum corneum lipids, consists of a mass of liquid crystalline material. Cross-polarised light microscopy has shown the multilamellar vesicles formed by lanolin are identical to those formed by human stratum corneum lipids. It is well known that the incorporation of bound water into the stratum corneum involves the formation of multilamellar vesicles.

Skin bioengineering studies have shown the durational effect of the emollient (skin smoothing) action produced by lanolin is very significant and lasts for many hours. Lanolin applied to the skin at 2 mg/cm2 has been shown to reduce roughness by about 35% after one hour and 50% after two hours, with the overall effect lasting for considerably more than eight hours. Lanolin is also known to form semiocclusive (breathable) films on the skin. When applied daily at around 4 mg/cm2 for five consecutive days, the positive moisturising effects of lanolin were detectable until 72 hours after final application. Lanolin may achieve some of its moisturising effects by forming a secondary moisture reservoir within the skin.

In other studies, the barrier repair properties of lanolin have been reported to be superior to those produced by both petrolatum and glycerin. In a small clinical study conducted on volunteer subjects with terribly dry (xerotic) hands, lanolin was shown to be superior to petrolatum in reducing the signs and symptoms of dryness and scaling, cracks and abrasions, and pain and itch. In another study, a high purity grade of lanolin was found to be significantly superior to petrolatum in assisting the healing of superficial wounds.