What is lanolin?
Lanolin is a natural product obtained from the fleece of sheep and is used in a variety of topical therapeutic and cosmetic preparations.
It is a complex mixture mainly composed of high molecular weight esters (>80%), along with aliphatic alcohols, fatty acids, sterols, and hydrocarbons. Free alcohols are considered the main sensitisers in lanolin.
The term lanolin is derived from the Latin terms lana (‘wool’) and oleum (‘oil’); sebum is extracted from sheep’s wool, cleaned, and refined. A variety of different terms are used to refer to lanolin (and its components and derivatives), such as wool alcohols, wool fat, anhydrous lanolin, amerchol, lanolin alcohol, alcoholes lanae, wool wax, and wool grease.
Lanolin is the 2023 American Contact Dermatitis Society (ACDS) Allergen of the Year, named due to the increasing frequency of allergic reactions.
Where is lanolin found?
Lanolin, which usually acts as a protective coating in the fleece of sheep, is a good emulsifier and is found in many pharmaceutical preparations, cosmetics, and toiletries. It also has industrial uses eg, applied to metallic surfaces to prevent corrosion.
Table 1. Uses of lanolin
Who gets contact reactions to lanolin?
The prevalence of lanolin contact allergy is debated. In patients with dermatitis undergoing patch testing, positive patch tests rates are between 1.7 and 3.3%. Some studies have found a female predominance. The rate of contact allergy to lanolin in the general population has been estimated to be lower (<0.5%).
Those with broken or compromised skin due to pre-existing dermatitis (eg, venous eczema, atopic dermatitis) or wounds (particularly leg ulcers) appear to be at higher risk of sensitisation to lanolin. Because of this, contact allergy to lanolin is slightly more common in children (higher rates of atopic dermatitis) and the elderly (higher rates of atopic and venous eczema, and lower limb ulcers).
What causes contact reactions to lanolin?
Allergic contact dermatitis (ACD):
- Type 4 or delayed, immunological, hypersensitivity reaction that occurs 48–72 hours after exposure to the allergen
- May occur unexpectedly after the allergen was previously well tolerated
- Following sensitisation, ACD can arise with minimal exposure.
- Non-immunological reaction that develops when an agent damages the skin surface faster than it can be repaired
- Often occurs following repeated exposure to an irritant
- More common than allergic reactions to lanolin.
What are the clinical features of contact allergy to lanolin?
- Localised erythema, pruritus, swelling, or blistering hours to days after contact with a topical product containing lanolin.
- Reaction location dependent on application site; commonly affected areas include the face, hands, and arms.
- Skin with pre-existing dermatoses appears to be more likely to react or deteriorate concomitant with the use of a topical agent containing lanolin.
- Lanolin can also cause irritant contact dermatitis and contact urticaria.
How do clinical features vary in differing types of skin?
In the United States, non-Hispanic black patients are less likely than their non-Hispanic white counterparts to be allergic to lanolin.
What are the complications of contact reactions to lanolin?
- Aesthetic concerns.
- Secondary skin infection eg, bacterial skin infection.
- Disseminated secondary eczema (autoeczematisation).
- Postinflammatory hypopigmentation or hyperpigmentation.
- Lichenification can result from chronic inflammation due to contact dermatitis.
How is contact allergy to lanolin diagnosed?
Contact allergy to lanolin is diagnosed by patch testing. However, patch testing preparations vary, with no universal consensus. The composition of lanolin can also vary between different sources, breeds of sheep, geographical locations, extraction methods, and chemical modifications, making representative patch testing a challenge.
Commonly used patch testing regimes include one or more of the following:
- 30% lanolin alcohols in petrolatum (traditional ‘gold standard’)
- 50% Amerchol L101 in petrolatum
- The patient’s own lanolin-containing product/s.
Repeated open application tests (ROAT) may be useful for patients with questionable or weak reactions to patch testing.
What is the differential diagnosis for contact reactions to lanolin?
Potential types of contact reactions to lanolin include:
Depending on clinical presentation, other differential diagnoses to consider include:
- Other forms of dermatitis and eczema (eg, atopic dermatitis, photocontact dermatitis, dyshidrotic eczema (pompholyx), asteatotic eczema, seborrhoeic dermatitis, discoid eczema, or stasis dermatitis)
- Skin infection (eg, bacterial or fungal)
- Drug eruptions
- Cutaneous symptoms of underlying disease (eg, systemic lupus erythematosus).
What is the treatment for contact reactions to lanolin?
As with other contact reactions, once lanolin has been identified as an allergen, education and avoidance are the cornerstone of treatment and prevention.
Product labels should be checked for ingredients and products containing lanolin avoided. Lanolin and its derivatives are also known by several other names. These include:
- Adeps lanae anhydrous
- Aloholes lanae
- Anhydrous lanolin
- Wool alcohols
- Wool fat
- Wool grease
- Wool wax.
What is the outcome for contact reactions to lanolin?
Symptoms usually settle once the allergen (or irritant) is identified and avoided. Ongoing exposure (eg, at work) can cause chronic symptoms.