Is it OK to scratch dandruff off the scalp or will it cause scarring and hair loss?

Scratching is a normal human response to itching. Billions have scratched throughout evolution without necessary causing hair loss. Scratching can cause hair breakage. The only concern is if the scratching is very excessive. This can cause inflammation, rarely infection  and very very rarely irreparable damage.

A better way to deal with seborrhea is the shampoo with 2%ketoconazol and massage triminicolone 0.1% cream  or use a steroid creamto massage into areas of itching and scaling as needed.

Constant scratching of the scalp puts you at risk for losing hair from a constant pull. This condition is called traction alopecia, so don't scratch just use appropriate anti-dandruff shampoos