Yes, SENSITIZED is a Scrabble word!

Letter values in Scrabble US: S 1, E 1, N 1, S 1, I 1, T 1, I 1, Z 10, E 1, D 2.

Is it a valid word?

SENSITIZED is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

make sensitive or aware
cause to sense; make sensitive
make sensitive to a drug or allergen
make (a material) sensitive to light, often of a particular colour, by coating it with a photographic emulsion

having an allergy or peculiar or excessive susceptibility (especially to a specific factor)

Not playable in Scrabble US: SENSIFY, SENSIBILIZE, SENSIBILISE, HYPERSENSITISED, SUPERSENSITIZED, SUPERSENSITISED.