I have very itching sensation in my inner thighs and a lot of scratrch marks are there due to scratching... also itching sensations are there in my scrotum... only if I statrt scratching... itching sensation begins... what to do.. when I apply sebonyl cream... marks are gone... but still itching occurs somethime

Try taking flaxseed oil.

Is there a possibility you could have crabs which is a sexually transmitted parasite. Your description fits and they would be irritated by scratching and bite all the more:

www.emedicinehealth.com/crabs/article_em.htm

So how do u get rid of crabs