Hey boron, saw u after long. That's totally normal for skin to wrinkle after prolonged exposure to water. When the oil is washed-up after prolonged exposure water enters the skin through dead keratin and this creates swelling and wrinkling of the skin. As a result dead keratin may partially separate from the normal skin (if exposed for long it gets exfoliated) that might cause numbness of the skin.
Here is the different story
http://news.discovery.com/human/evol...wet-130109.htm