Hello, I'm really sorry to hear about Illyria's small scabs and excessive scratching.
The little bumps that you are feeling are his skin's reaction to an allergy or irritant and are called miliary dermatitis.The most common reason for these symptoms is flea allergy dermatitis. Flea allergy dermatitis is horrible. In allergic cats it only takes one bite a month for them to itch like crazy. If you don't see any fleas you might not have a huge population. If you have other pets who aren't itchy they may not be allergic. You must use flea control every 3 weeks in an allergic cat. Many over the counter products have a problem with fleas being resistant and some can be down right dangerous. I neverrecommend any products that Hartz or Sargent's make. I recommend Advantage orFrontline Plus every 3 weeks for at least 4 months if everyone is indoor only or consistently if any pets go outside as they will be a continual source. All pets in the house must be treated as if you don't the nonallergic ones serve as a flea reservoir for the allergic one and you'll never solve your problem. Inhaled allergies (to pollens, dust mites or mold spores) are another possibility.To control allergic symptoms (flea allergies or inhaled allergies) you can try:
1) Benadryl (diphenhydramine only, the combination products with decongestants and acetaminophen are toxic to cats) at 1mg per pound every 8 hours. That's a half of 25mg tablet every 8 hours for a cat that is 8 to 15 pounds.
2) Chlorpheniramine at 4mg once or twice daily.
Combined with high doses of omega-3 fatty acids antihistamines work to relieve heritchiness. I like 3V caps or Derm Caps. Together antihistamines and omega-3 fatty acids work synergistically. These should help reduce the itch. Be aware that antihistamines can cause drowsiness or hyperactivity which should resolve with continued use.
Food allergy is another reason for excess grooming and itchiness especially around the face neck and ears. You might wish to try a hypoallergenic food for 8 weeks or so. My suggestions are Hills Z/D or Royal Canin Duck and Green peas. She will need to eat only that food, no other treats or foods during her food trial. You should see an improvement in 8 weeks but full effects may not be seen for 12 to 16 weeks.
You can also use cortisone cream or spray on especially itchy areas as long as they aren't raw.If there are other cats in the home that she doesn't get along with or outdoors that upset her perhaps this is stress related. If so a product called feliway, which is a synthetic version of a calming feline pheromone, may help. You can purchase this from petstores or online.If she goes outside other parasites like Cheyletiella or sarcoptic mange are possible causes as well.For now I would start with excellent flea control, an antihistamine and omega 3fatty acids. If she's not significantly better in 2 weeks then it's time for a veterinary examination to look further for problems and/or a hypoallergenic food trial.
Please let me know if you have further questions by replying to this post.