I had 4 children..I'm not an expert in any way of my suggestions.... But I used calamin lotion and it helps!! You need to determine if he is not ALLERGIC to flea bites{as silly as that sounds its true,they can be} If it is an allergic reaction there will be fevering..{one of mine was allergic} Benedril helps with the itching if you want too..good luck!!
My dad used to treat our various insect bites with witch hazel. It is relatively easy to find, in any department store or pharmacy. I don't remember stinging, from the witch hazel. I however would suggest a test spot. You could even use the witch hazel as a cleanser, it also draws out inflamation, then use the other persons suggestion of calamine, it is a drying agent. Trust me in 12 years of pet grooming I have seen horrible infestations. A few things I have seen work are, washing the animal in antibacterial dish soap, they fall off dead, in masse. Be certain you thourghly rinse all soap out. Next is a product call Adams flea spray, saturate your carpet, rugs animal bedding, pretty much everything, because if an area is left untreated, thats where they will all gather. Wash as many things as you can, remembering how much animails like to lay on piles of clothes ex. kids rooms. Next is a natural remedy, you still have to be very careful with, its called tea tree oil, it comes consentrated, put no more than 2 drops in dogs shamppoo, also in kids body wash/shampoo. This will keep most every insect off, including mosquitoes, and headlice. I assure you this stuff really works. However don't be tempted to use more, in small amounts it smells okay but by adding a third or fourth drop, the smell is god awful, it can also be irratating too the skin and definatley the eyes, if you use too much. I hate too admit this but last year my eldest daughter contracted lice 3 times, the doctor said some hair types are ideal for them little suckers, especially very clean hair, At my wits end I tried this and so far she hasn't had them since, even when our neighboors kids got them. I also had positive results with animails I've treated, sounds like your cat has extreamly irrated skin, this would be a better treatment, because of the harshness of all pesticides, after the cat heals definatley treat him with a commercial product like frontline or advantage. Also seven dust (you can pick it up at any farm supply store) is extreamlly effective for treating your yard, under the porch, on the porch, anywhere the animal laid or hid. My sister had this same problem, after much trial and error, this was the combo that worked for us. Good fortune