Hello, thanks for your question today! I am Dr. Drew, and I am a licensed veterinarian. I'll be happy to help you in any way I can.
Piriton or Piritese are both acceptable for use in cats, at a dosage lower than would be used in a human.
Typically, 1/4 tablet of either would be a reasonable starting point, going up to 1/2 tablet if no improvement is noted.
For Piriton, that typically means starting at 1mg, and going up to 2mg if needed. The Piritese starts at 1.25mg, and goes up to 2.5mg.
Either of these can be given every 12 to 24 hours.