Adult autistic son unable to eat

Can anyone help, please?

My 25 year old autistic son has relatively low support needs, although he is unable to hold down a job.

Recently he has really been struggling to eat and this is causing him anxiety, which makes the problem worse.

He gets hungry,  but has no appetite and develops a dry mouth and this makes swallowing impossible.

He's  eating very little and even once palatable foods don't appeal any more.