Table 5: Skin irritation effect of different chemical enhancers.

Chemical enhancer with concentrationSkin irritation

Citric acid (2.5%) 0
Oleic acid (5%) 0
Isopropyl myristate (10%) 0
N-lauroyl sarcosine (2%) 2
Tween-20 (2%) 1
Transcutol (20%) 1
Dimethyl sulfoxide (10%) 2
N-methyl pyrrolidone (10%)3