Hubby itchy after eating high protein dinner in the evening

[1ily]

My hubby becomes very itchy after having dinner - high protein in the evening. He has protein drinks during the day and protein in his lunchtime meal but the itching doesn't start until after his evening meal about 7pmish- strange!We know it's to do with toxin build up from the ammonia produced from breaking down the proteins so he takes quite alot of lactulose ( 80 ml / day) to try to aid the body to get rid of the toxins asap.

We would really appreciate any advice to help us to try to stop his evening inching issue.

Thank you in advance for using your time to reply to this. Kindest 1ily