I'm sorry that your question wasn't answered in a timely manner. I don't know of any mechanism in which worms would cause such a sensitivity. You appear to be inducing an itch reflex by touching Tom's torso/back. His biting his front legs is a displacement behavior; in other words, although he's sensitive where you're touching him, he's choosing to attend to his legs instead. Pruritic (itchy) extremities are seen when either atopy - allergies to environmental allergens such as pollens, molds, dust, and dust mites, etc. - or a food intolerance has arisen and so Tom may well be itchy not only where you've been touching him but also on his extremities. I'm going to post my synopsis of the pruritic cats for you. Please take your time perusing it and then return to our conversation with further questions or concerns if you wish...
I'm sorry to hear of this with Tom. Pruritic (itchy) cats are suffering from an allergic dermatitis the great majority of the time. Allergies to flea saliva, environmentals such as pollens, molds, dust and dust mites, and foods should be considered. In rare instances the mange mite Demodex might be responsible.
Our dermatologists tell us to apply an effective over the counter flea spot-on such as Advantage or a fipronil-containing product such as Frontline or one of the newer prescription products available from Tom's vet even if fleas aren't seen. Cats can be such effective groomers so as to eliminate all evidence of flea infestation. Indoor cats can contract fleas because we walk them in on us and flea eggs and larva can remain viable in your home for months. Turning on the heater or As the weather warms at this time of year then hatches the eggs. Flea saliva allergy is usually most evident on the saddle area – the area between the edge of the rib cage and tail. In severe cases, an anti-allergenic prescription corticosteroid such as prednisolone will work wonders for cats allergic to the saliva of the flea. Your other pets may not be allergic to the saliva of the flea.
Environmental allergies are usually addressed with prednisolone as well. In some cats an over the counter antihistamine such as chlorpheniramine (Chlor-Trimeton) dosed at 2mg/cat daily or diphenhydramine (Benadryl) dosed at 1-2mg/lb twice daily may be effective.
Food intolerance/allergy is addressed with prescription hypoallergenic diets. These special foods contain just one novel (rabbit, duck, e.g.) animal protein or proteins that have been chemically altered (hydrolyzed) to the point that Tom's immune system doesn't "see" anything to be allergic to. The over the counter hypoallergenic foods too often contain proteins not listed on the label - soy is a common one - and these proteins would confound our evaluation of the efficacy of the hypoallergenic diet. There are many prescription novel protein diets and the prototypical hydrolyzed protein diet is Hill’s Prescription Diet z/d ultra (I prefer a hydrolyzed protein diet). We usually see a positive response to these foods within a few weeks if we’ve eliminated the offending food allergen. A food intolerance can appear at any age and even if our cats have been eating the same food for quite some time.
We used to diagnose these cats with psychogenic alopecia - a neurotic over-grooming - but have come to realize that most of these cats truly are allergic cats. Feline psychogenic alopecia is overdiagnosed but does exist. Excessive and out-of-context grooming is thought to be an obsessive-compulsive behavior that's triggered by environmental stresses and anxiety. The condition is uncommon in cats, with purebred cats that have high-strung nervous temperaments being possibly predisposed. This type of alopecia may occur anywhere on the body where the cat can lick but it most commonly involves the medial forelegs, inner thighs, perineum, and ventral abdomen. Hair loss is often bilaterally symmetrical but remaining hairs don't epilate easily. The top differentials are flea allergy dermatitis, food allergy, dermatophytosis (fungal infection), other ectoparasites (mange) and atopy (allergies to environmental allergens such as pollens, molds, dust, and dust mites, etc.).
The underlying cause of the psychological stress (e.g., separation from owner, moved to a new house, animal companion died, new pet in household, formerly outdoor cat denied access to outdoors) must be identified and appropriate environmental modifications made, if possible. A good flea control program should be instituted to prevent fleas from aggravating the symptoms. Use of a mechanical barrier (e.g. Elizabethan collar, T-shirt) for 1-2 months to prevent grooming may help break the habit. Behavior-modifying drugs may help stop the abnormal grooming behavior. In some cases, treatment may be discontinued after 30-60 days of therapy; in others, lifelong therapy is required for control. Drugs that may be effective include the following: amitriptyline, clomipramine, buspirone, phenobarbital, diazepam, and naloxone.
Please note: Tom's vet can prescribe a topical product that worms Tom. You wouldn't have to dose him orally. Please note, too, that the pruritis of atopy is likely to be seasonal' not so a food intolerance.
Please respond with further questions or concerns if you wish.