First, I would be suspicious that we have more than one issue present. This is because while allergies can cause sneezing and skin irritation; we rarely see an allergen that causes both (unless we have a dusty litter or one of those examples I noted –which is less likely here). So, we may have 2 allergens but I’d be more suspicious that we could have a skin allergen and that the immune reaction is distracting the immune system such that we have a flare up of a feline viral agent (ie herpes) to cause the sneezing.
Now focusing on the skin, if we have all three cats signs and Otis is out of the house, this does sound like a possible infectious issue. A potential group exposure (topical or ingested) could appear this way but generally speaking we don’t tend to see common allergies affect all cats in the house unless the trigger is a generalized skin irritant. But if those can be ruled out, then we’d lean away from an environmental allergen.
With those aside and considering their target area on their skin, a flea allergy dermatitis or mites/lice infestations could certainly appear this way. As well, the latter would not necessarily respond to steroids (which often treats the allergic reaction but cannot remove the trigger and therefore won’t settle signs if the cause is still ongoing).
With that all in mind, I would consider using a multi-species anti-parasitic treatment for all the cats. Ideally, we’d want to have the local vet dispense Advantage Multi, Stronghold, or Revolution. They should have no issue dispensing these if they have recent weights for the kitties. These can be used every 2-3 weeks for a few doses to help remove any mite and lice concerns. It would also address their fleas, so they can hold off on their oral treatment for the short term. And that way we can rule out and/or address our suspect parasitic concerns.
As well, to just cover bases against allergies without immune suppressing the cats (and issue with the steroids any why a viral upper airway infection or mite issues could get worse or not settle with steroids), we can consider a trial on an OTC antihistamine. Most commonly we use Benadryl/Diphenhydramine (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/diphenhydramine-benadryl). A low dose (ie. 0.25mg per pound of their body weight twice daily) can just be enough to manage allergic irritation. Alternatively, you can also use Cetirizine (just 5mg for a cat) once daily. For either, we like to keep the dose low, since it can cause drowsiness (just like in people).
Finally, just in regards ***** ***** sneezing potentially related to the cats being herpes carriers, we can consider also treating with L-lysine. This is an OTC nutritional supplement that can help reduce viral load. This is available over the counter at health food stores, pet stores, and the vets. They tend to come as gels, powders, or crushable tablets to mix into food. An average cat dose is 500mg a day. So, we could use this as well.
Overall, we can see these signs related to a few different issues. That said, its quite rare to see multiple cats show allergic signs to pollens and standard allergens. And even less common to see it when cats are split into separate houses. Therefore, we'd be best to treat for mites/parasites here. As well, we can also use the other supports to reduce irritation as we work to determine the root irritant and clear it for all of them.
Please take care,
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