In simple terms this will mean that he feels an irritation in the skin and there may be a very simple solution to this. In particular if this has just started and is a first episode that may be all there is to it. However there is a reasonably common problem in cats that can cause these signs. The condition is called Feline Hyperesthesia syndrome. It is a little complex so I will go through the whole thing with you.
This is a well recognised problem in adult cats. The classic sign is irritation towards the rear end (tail, dorsal back and flanks). Usually there is agitation and signs of distress or fear. Cats will run and hide as though there is something frightening them. On occasions there can be self mutilation in particular involving the tail. Many cats will exhibit rippling of the skin particularly if petted.
The cause is not fully understood but seems to be triggered by one of or a combination of behavioural, neurological, and dermatological factors. The dermatological influence can usually be easily tackled and if this is the first episode hopefully it will be as simple as this. So ensure there are no fleas by using a top quality spot on flea control medication like Revolution or Frontline. Also consider any changes in feeding or environment that may have introduced a new allergen to cause an allergic dermatitis. Hypoallergenic diets can be worth trying (available through vets). With the behavioural side of things we need to consider anything that may be causing anxiety. That means social stresses like a new cat in the neighbourhood and changes within your home (feline or human). So consider if your cat seems extra nervous or upset lately. Occasionally there may be a neurological cause. This includes forms of epilepsy. There has been some suggestion that a form of myositis (inclusion body myositis, an autoimmune disease of the muscles) may occasionally be a cause. I have also seen some good results with acupuncture. But make sure you use a certified veterinary acupuncturist. Now the more standard treatments for this condition vary depending upon what is thought to be the cause. So: 1. Dermatological cause we must try to eliminate the cause (allergy, fleas) and use predinisolone to suppress the allergy. 2. Neurological (seizure ) we will use anti-seizure therapy (usually phenobarbitone) 3. Behavioural. I usually use amitryptiline (Elavil), fluoxetine (Prozac) or clomipramine (Clomicalm). The difficulty is often establishing the cause and sometimes we need to work our way through the treatment regimes.
So I’ve mentioned a lot of things here to try to cover all the causes and treatments. Very often only a single part of this is relevant to an individual cat. First check for fleas or evidence of dermatitis. If that is negative start to look at the other possibilities with your vet. I hope I have been of some assistance. Please contact me back if I can assist further Kindest regards, Peter