Extreme dandruff and hairfall problem for 24 year old male. oil builds up on hair if not washed daily.

Seborrheic dermatiti: It sounds like you are describing seborrheic dermatitis. Seborrheic dermatitis causes an itchy, inflamed, scaly scalp that can contribute to hair loss. Start by using an over the counter shampoo for dandruff (one with zinc pyrithione or tar would be most helpful) and leave it on for 10 minutes prior to washing off. If you are still having problems, see a dermatologist for a prescription.