Skin Sores, Lumps, Abscesses
This is the most commonly seen side effect with GS likely due to the low pH.
These can look quite ugly but generally heal well by themselves or with little intervention. In some cases, the sores have been quite large but it is extremely rare for cats to have require surgery for resolution. We recommend generally leaving sores alone other than removing hair from around the site, disinfecting it and preventing the cat from scratching/licking it. Some owners have had positive results with Duoxo calm or chlorhexidine mousse or Vetericyn spray or tropical skin healers. Many cat owners whom their cats on FIP treatment decide to put shirts or recovery suits on them to prevent scratching or otherwise disturbing sores.
Usually this is adipose tissue and does not require any intervention.
These are often sterile but occasionally are infected and require a course of antibiotics
Allergic reactions to FIP antiviral medications are very rare but occasionally reported. In most cases the allergy appears to be to something in the drug preparation other than the antiviral itself, therefore switching to a different formulation or administration method (ie. injection to oral, or vice-versa) often resolves the issue.
The most common allergy manifestation is a rash, pruritus, acne, or other skin conditions. In some reported cases it has been fairly severe.