I am sorry your boy is not feeling well. It is possible a steroid will reduce the congestion and increase appetite. There are other thins you can do.
Make a steam room by running a hot shower in your bathroom. Take him in for ten minute intervals to break up congestion.
Give him L-lysine.
Offer very odorous foods like tuna, salmon, sardines, warm canned cat food or baby food with no onion powder.
Feed small amounts every two hours as that is the best way for his body to metabolize calories and put weight back on.
He can also take antihistamines.
You can 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 he 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).
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