Some cats get raised bumps or rashes at injection sites. These rashes are very noticeable if you’re doing daily subq fluids, but can occur any time a cat receives an injection or has blood drawn. If your cat experiences these bumps and rashes it’s very possible that they’re allergic to needles.
Hypodermic needles are made from stainless steel, which contains a very small amount of the metal nickel. Allergies to nickel are very common in humans and in animals. For most people and pets the amount of nickel released during an injection is small enough that it does not cause a reaction, even if they have a known nickel allergy.
With subq fluids, the needle is in place longer than for a simple injection. The extra time the needle spends in the body increases the risk of allergic reaction.
How To Treat
One of the easiest ways to calm the reaction process is to put a small amount of topical hydrocortisone cream or ointment on the are where the needle had been inserted. You would do this after the the needle has been removed.
Silicone Coated Needles
Needles with silicone coating have a reduced reaction rate compared to non-silicone coated needles.
I couldn’t find info on the “human” Terumo needles to see if they’re silicone coated. Their “Sur-Vet” veterinary needles do say they’re silicone coated.
Covidian, BD, and Care Touch all make silicone coated needles. Many local pharmacies carry BD brand needles in stock. You might want to try needles that specifically say they’re silicone coated to see if kitty has the same reaction. But do this in a different spot, nowhere near the existing reaction. Depending on where you live you may be able to purchase needles without a prescription. The pharmacist will limit the amount they sell to maybe 5 needles, but that should be enough to do a good test for reaction.