This is an allergic reaction called Miliary dermatitis. It is not contagious, hence other cats are unaffected.
You can apply raw honey to any sore or irritated areas. It is a remarkable healing agent:
In addition, add one quarter of a 4 mg chlortrimeten to a tablespoon of baby food chicken or turkey with no onion or garlic.
Give it every 24 hours. It is very tiny so she will not detect it
Any of these are also acceptable:
Benadryl at a dose of 1/2 of a 25 mg tablet given twice daily or
Chlorpheniramine at a dose of 2-4 mg twice a day or
Claritin (Loratadine) at a dose of 2.5-5 mg/cat or
Zyrtec (cetirizine) 5 mg once or twice a day
It is important to ensure that the formulations used contain ONLY the antihistamine and are not combination products (e.g. Claritin-D contains pseudoephedrine, which could cause very significant adverse effects in a cat).
Please let me know how she is doing. Just reply here or if you prefer, we can speak on the phone.
Please be so kind as to rate my answer with positive feedback, as that is the only way I receive recognition from the site for my assistance. Thank you!
Providing a positive rating will not end our conversation, should you need me for any follow-up. Simply click 'Reply' for clarification or additional information, if needed and I will always be here for you and your kitty.