Skin reflectance and colour values measured with reflectance instruments are not absolute data but depend on the aperture area of the measuring head. This is probably due to variations in the proportion of longer-wavelength light reflected from the skin and collected by the instrument.

Allergic reactions to toothpaste flavours are infrequent: only 5 cases in a 26‐year period among 46,000 Copenhagen eczema patients (9) and 7 cases in a 6‐year period at Gentofte Hospital (3). Spearmint is used in almost every brand of toothpaste as a flavour, together with other flavouring ingredients such as menthol, peppermint, anethole, eugenol and cinnamic aldehyde. It is also used in chewing gum, medicines, etc.

The aim of the present study is to examine the availability of MR FT Raman spectroscopy in the clinical evaluation of positive allergic and irntant or doubtfiul patch test reactions. Instrumental measurements at 42 positive patch test sites in 16 patients were compared visually and evaluated at 48 h and 72 h in order to examine the sensitivity of this method to detect the biochemical changes occurnng at the sites of the patches. Raman spectra of nonna! control skin and skin reacting to patches on the back were obtained with an FRA 106 Ranian module on a Bruker IFS 66 optics system (Bmker, Karisruhe, Germany). The most significant changes in the spectra were detected in the region specific for water content and protein structure in both types ofreactIons at 48 h and 72 Ii, compared to nonnal skin. Calculated relative water content for irritant or doubtful reactions was as 0.37 (control) < 0.42 (48 h) < 0.51 (72 h) and for allergic reactions as 0.37 (control) < 0.59 (48 h) < 0.58 (72 h), with a statistically significant difference between the 2 reaction groups at 48 h (Wilcoxon'.s test). Protein structure changes differed mostly after 72 h in allergic reactions at 1244 cm' (amide I) and at 937 cm (protein backbone vibration) Our findings indicate that technical reproducibility of NIR FT Rainan spectroscopy by means of measurng of water content was the best to enable a precise noninvasive evaluation between 2 types of patch test reactions, and provided continuous data grading of reaction intensity suitable for clinical studies.

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