Hello, my name is***** and I have over 20 years of experience as a veterinarian.
I'm sorry to hear that your fellow Frankie is suddenly restless, panting and licking. This represents discomfort and sounds like an allergic reaction.
This is usually related to an insect or spider bite or sting. Sometimes we never figure out the cause because the bite/sting isn't obvious, just the systemic reaction to it is.
Treatment is based upon stopping further allergic reaction with antihistamines like Benadryl or Chlorpheniramine, and sometimes cortisone if the reaction progresses.
Any vomiting or diarrhea?
I know he is panting but that can be a stress response. Any difficulty breathing secondary to throat or facial swelling?
Are his gums and tongue a nice bubblegum pink?
You can give him an antihistamine, either:
1) Benadryl (diphenhydramine only don't use the combination products with decongestants or acetaminophen as they can be toxic for cats) at a dose of 1mg to 2mg per pound or one half of a 25mg capsule per 8 to 15 pounds of body weight orally every 8 hours. Benadryl is very bitter and some cats will drool excessively or may even vomit because of that. That doesn't mean it is making him ill, he just hates the taste. If that's the case with him try a different antihistamine.
2) Chlorpheniramine at 4mg twice daily.
3) Zyrtec (Cetirizine hydrochloride) at a dose of 5 mg per cat given orally every 24 hours. Make sure it is NOT the formulation with a decongestant (such as Zyrtec-D) because cats cannot tolerate decongestants.
You'll need to give it for at least 72 hours (3 days) to allow the allergen time to clear. If you stop too soon the reaction will recur.
Cats take a really high dose of antihistamines compared to people, so don't let the amount worry you. They require more than we do per pound of body weight. These may make him a little sleepy.
You can also give him a cool water spot bath with an oatmeal based shampoo to soothe his skin. The cool water will close skin capillaries and reduce inflammation and oatmeal reduces inflammation. Lather gently, let it sit for several minutes and then rinse with cool water.
Since he is licking a particular area you can apply cortisone cream (like Cortaid) to that area.
And then you'll need to watch him closely for any progression of symptoms. That includes difficulty breathing due to throat swelling, vomiting or diarrhea.
The itchiness should resolve slowly over the next 12 to 24 hours. In extreme allergic reactions they can get shocky and collapse but you should see difficulty breathing and vomiting/diarrhea first. Those types of severe reactions are very rare.
Most reactions are managed just fine with antihistamines alone.
Because you know now that he has these types of reactions you should keep an antihistamine on hand at all times.
If you notice progression of his symptoms don't wait, have him checked on an emergency basis. If you'd like you can have him examined by an emergency veterinarian now. They can give a cortisone injection which will lessen symptoms faster.
But if he seems to be doing well then I would just call your regular veterinarian Monday and let them know so it is on his record for future reference.
Please let me know if you have any further questions.