I am sorry your fur kids have upper respiratory infections. It is airborne and very contagious among cats,
The good news is yes, they can all be treated at home.
They can take any of these antihistamines:
add one quarter of a 4 mg chlortrimeten to a tablespoon of baby food chicken or turkey with no onion or garlic.
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).
In addition, add 500 mg of l-lysine to the community water or get these:
Feed them smelly canned foods or tuna so they will keep eating.
If they get dehydrated drain the water from a can of tuna and let them lap it up.
If anyone is congested make steam room by running a hot shower in your bathroom. Take them in for ten minute intervals.
Please let me know how they are doing.
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