AMINO ACID METABOLITES IN DRY SKIN 189 z [•_ 30 20 10 a) • • Ser • Cit • o His Asp 2 3 TIME [•.K] 30 20 10 b) Set Cit Asp Orn L¾s 2 3 TIME Figure 3. The influence of experimentally induced hyperkeratosis on the free amino acid composition. a) = control b) = treated. Dry skin in winter. Of 77 subjects, the cheek skin was estimated as dry skin (A) in 25, accounting for 32% of the subjects. This suggests that skin gets chapped in winter in a considerable number of people (Table III). Amino acids and their metabolites were measured in 46 subjects, including 16 having dry skin (A Group), 22 with an inter- 30 o Pro AspThr Ser Cit Glu GI, Ala Val lie Leu Tyr Phe Orn Lys His Arg Figure 4. The free amino acid composition of human forearm stratum corneum 7 days after application of 3% LAS solution. Open bars = control solid bars = treated.

190 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS F---I • F--- Serl I His I I Gly• • Glu • I Ala • • Asp I I • I Tyr Pro I • I Cit• • Orn I • Arg • PCA I Leu Phe Thr Lys NON-ESSENTIAL AMINO ACIDS ESSENTIAL AMINO ACIDS Figure 5. Changes in the composition of free amino acids and their metabolites in hyperkeratotic as compared to normal stratum corneum. 80 o c• o 1w 2) 60 lW 9oe 8O 70 3) TIME mol% 1W 90 70 uJ o uJ z • cD •• 1w 90 90 a:• ..O, ......,• 70 70 ' 1 2 3 "-' •- TIME t.._.:, Figure 6. The influence of hyperkeratosis on the formation rates of PCA, UCA, Cit, and Ala. (1) PCA/ PCA + Glu (2) UCA/UCA + His (3) Cit/Cit + Orn (4) Ala/Ala + Asp. Dotted line = control solid line = treated. Histograms are the average rates of conversion. (n = 3) Values are mean _+ S.E.