Relevance of positive reactions to wool alcohols

P.J. Frosch (Dortmund)

Lanolin is a natural product from sheep fleece and contains various esters and polyesters of high molecular weight alcohols and fatty acids.The composition varies from different sources. Furthermore, different modifications with suspected reduced allergenicity (dehydrogenated, acetylated l.) are on the market. The commercial test preparation – 30% wool alcohols in petrolatum – is also a complex mixture of esters and alcohols (aliphatic, steroid, triterpenoid) and fatty acids derived from hydrolysis of the oily, waxy fraction of lanolin.There is no universally accepted way of standardization for the production of this test material.

The general incidence of lanolin allergy in eczema patients is around 3% (1). Frequency of snesitization may be as high as 17% in elderly female patients with a long history of dermatitis, particularly in those with leg ulcers (2-4).

Controversy regarding lanolin allergy is based on various observations: Frequent false positive reactions; low reproducibility of positive patch tests after a long interval; rarity of lanolin sensitization when applied to normal skin and with cosmetic usage; lack of sensitization in experimental human and animal models with few exceptions (5).

A patch test reaction is considered as false positive, if a product containing the sensitizer is tolerated without adverse effects. However, we now know that allergic contact dermatitis is aslo strongly dose-dependent and influenced by various factors (location, skin condition, mode of application etc (6)). In regard to lanolin allergy it must be emphasized that great differences between the patch test preparation and the actual brand (s) of lanolin used by the patient may exist. A patient may have been sensitized by one product in the past, reacts to 30% wool alcohols in the patch test, but tolerates a cosmetic on normal or even diseased skin containing a different type of lanolin at a low concentration.

It is a specific feature of testing with wool alcohols that in many cases the reactions are weak positives (1+) and may be regarded as negative or doubtful/irritant by another investigator. The determination of clinical relevance in a certain patient with a positive patch test to 30% wool alcohols is therefore often difficult and requires a careful evaluation as follows:

Certain relevance

The patient has reacted to a lanolin containing product with a dermatitis on normal skin and/or with an exacerbation of eczematous skin (e.g. stasis dermatitis). This patient may tolerate another product with a low content or a different type of lanolin, unless he is highly sensitive.

Questionable/possible relevance

The patient has reacted to a lanolin containing product but other ingredients may also be the cause (e.g. a preservative or a fragrance). An exposure to a different lanolin containing product without the other ingredients may clarify the situation. If the ROAT is positive (usually performed on normal forearm skin for 2 weeks), clinical relevance obviously exists. If the ROAT is negative, relevance is probably non-existent. The patient´s sensitivity may be very low and a clinical reaction may only occur after long-term usage on dermatitic skin (or if certain cofactors exist, e.g. occlusion, high temperature, use of a product with particularly high concentration of the sensitizer(s)). If retesting at a later stage yields a negative patch test result to wool alcohols, the previous reaction is considered as an irritant one (e.g. due to the excited skin syndrome).

Unexplained/none

The patient has never reacted to a lanolin containing product or has never used one. The latter is unlikely due to the wide distribution of lanolin in various products for skin care beginning at early childhood. Retesting is recommended. If the positive test is confirmed, relevance may occur in the future. If positivity is not reproduced, irritancy is the most likely explanation.



References

1. Schnuch A et al: Contact Dermatitis 37:200-09 (1997)

2. Breit R, bandmann HJ: Brit J Dermatol 88:414-16 (1973)

3. Lange-Ionescu S et al: Dermatosen 44:14-22 (1996)

4. Gallenkemper et al: Contact Dermatitis 38:274-78 (1998)

5. Fregert S: Contact Dermatitis 10:16 (1984)

6. Menné T et al: Allergic contact dermatitis in man – experimental and quantitative aspects. In: Textbook of contact dermatitis. Rycroft R et al (eds), 3rd ed. Springer, Heidelberg (in press)