COSMETICS AND DERMATITIS . •¾wew of their immiscibility with oil. a consequence, they are unable to '•:•f. gain access to the living cells in the •ntact skin. Substances w•th surface- i?•!?active properties, such as triethano- :??!!:lamine, sodium lauryl sulphate and like, by reducing surface tension of large blisters in the epidermis. If the irritant is powerful enough, iU:Ch as a strong acid or alkali, i'•tual death or necrosis of the cells '•ill occur. Because of the pre- sident'dominantly fatty nature of the horny '•:•i:la•yer and the supernatant sebum, bile and oily emulsions are more (•?iikely to penetrate to the deeper •:• •i:aYers and thereby give rise to derma- •}•i'titis. This is why the essential oils some plants are irritants. On the •*-•?1øther hand, aqueous solutions are •?•!iess likely to give rise to trouble in ?•11i:•enable,water-soluble agents to pene- •iii? •rate deeper in the skin when they are ß ?i:incorporated in various vehicles It :!i::i•Should be remembered that, if a , ,:i!i!•high concentration of such a wetting ::'.•: agent is incorporated in a prepara- ?!-11: lion, this may lead to an und6sirable :.2 concentration of the active consti~ ::.!•::ituent at or below the prickle layer :'i:•:' and thereby give rise to a dermatitis, :!:..:whereas the same agent, incorpor- :i:i:.: ated in a simpler aqueous vehicle, might not penetrate so deep and nq trouble would ensue, ß CASES OF COSMETIC DERMATITIS Most of my audience must be familiar with a typical hair-dye dermatitis. The patient, nearly (Continued on page 207) The Mechanism of Sensitisation. Figure I (above) represents the entry of chromic acid through an abrasion in the skin. Note oedema _and rupture of the intercellular processes in •rickle layer. Figure 2 (below): The process further advanced, showing blister formation. See also figures 5, 6, and 7. \\ 205

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ' • ?/.?.:,.,., . .,.-.*'. •,,,'/..., .., ' i•'" i• '- ß : :• :-,:. • ,, . ,, :.: i,- -,?: .. , . .:"-"-•-•' •.,:'•.:.•½ •, '::.' ...,. :'•-'•'.-- --'---'-•½'•? :... :. '.' ::. !.• : ..*•,•:... ß ii .-5 •:.., •.. .9:.:' . ,- ß "!•, . FiEure 3 (above) and FiEure 4 (opposite page) illustrate an unusual case of allergic to a face cream, whtch hal•l•ened.to be a water-in-oil emulsion of the lanaiin derivative ty•e. !•atient did not himself use the cream: it was his wife's. The illustration above shows the ment of dermatitis on the side of the cheek. ß ß -206.