Sentinal
This is not an area of benefits that we advise on so I have to suggest that you get face to face advice about the issue.
Allowable expenses are those items required for the care of the claimant, this might include aids and appliances or treatment not covered by the NHS.
You would need to show that any holiday was for therapeutic purposes, this would likely need confirmation from the claimants GP.
It's really got nothing to do with ESA being in payment, the situation would be the same if they were not receiving benefit or they were working.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
