SPECIFIC LANOLIN ALLERGY 333 The second stage correction is to distinguish between secondary lanolin hypersensitivity and primary lanolin allergy of which lanolin is the initial and sole cause. The only distinctive criterion for primary lanolin allergy is, surely, when the symptoms disappear completely on cessation of contact with lanolin not only in skin care products but also with wool wax in clothing or other commodities. Schwarzreid (26) noted that some types of eczema can be aggravated or sustained by contact with wool wax in clothes, and Sulzberger and Lazar (11) made a similar postulation. It is possible, however, to derive from the literature an approximate ratio between secondary and primary hypersensitivity in certain groups of patients. Thus Wereide (9) referred to 'several' specific hypersensitivities out of a total of 270. A quantitative proportion was given by Hjorth and Trolle-Lassen (10), namely 17 out of 50. Another by Reichenberger (25) who found 28 out of 97 by Stolze (35), 11 monovalent reactions out of 52 Epstein (22), 1 out of 5, and by Hjorth (17) who, in a small selection of patients, found a much higher figure of 19 out of 25. Including even the latter figure a weighted average of these quantitative results yields 33.18•o as the proportion of lanolin hypersensitivities which are monovalent and specific. Applying this second correction to the minimum and maximum first stage factors of 2.5 and 15 we obtain overall correction factors of 7.53 and 45.21 respectively which, applied as divisors to the average gross incidence of 65.9, yields a range of primary specific lanolin allergy amongst the general population of 1.46 to 8.75 per million. Residual errors The foregoing range takes no account of the fact that some patients may be treated by general practitioners without being referred to skin clinics. A compensating error is the deliberate inclusion of exaggerated figures in the stage two correction. Finally, there is an error inherent in estimating the population area served by a hospital. If we assume this to be 4-11.1 •o as in the case of Wycombe, the corrected range of incidence extends from 1.3 to 9.7 which can be expressed as 5.54-4.2 per 10 ø. Thus, the general incidence of specific lanolin may be said to be, at the most, 9.7 per 10 ø without making any deduction for test material which could have been autoxidized, distinguish- ing between lanolin from different manufacturers, or eliminating test results from subjects with abnormal skin conditions. The likelihood is that the true figure is considerably less than this calculated upper limit.

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